well after conversation with Mav i decided no make this tutorial, but after conversation with ThePanda i decide again make it also with suggestions of Darth_Spiderpig and Delta-1035 well there become!! :P

[size=150]A) STEP 1: Getting right MODL chunk
B) STEP 2: Putting into our model
C) STEP 3: Adding Texture for our MODL chunk into new model[/size]

NOTE: as example i will hex edit DarthD.U.C.K. Holsters with DC-17 Version and ep3trooper as model so you will need them also need XVI32 Hex Editor

A) STEP 1: Getting right MODL chunk
Open the file rep_addon_dc17holster_l.msh using XVI32, now we must find the correct MODL chunks so the First MODL called dummyroot_holster1 he isn't so go to the Second MODL is called SV_1 (this is the shadowvolume of holster for this reason say SV_ ) in this case we only want holster not his shadow so go to the Third MODL called Holster congratulation we found right one xD, but wait search next MODL (fourth MODL) is called Polymsh6 we must hex edit both MODL because MODL holster = holster and MODL polymsh6 = pistol part so we must select since the the M of MODL word of the Third chunk (remember called Holster) until letter previous to CL1L word in this case letter is one square so with Third and Fourth MODLs select (marked in red) press CONTROL + C (copy) and open new window of XVI32 go to FILE - NEW and press CONTROL + V (paste) , into new window where you pasted them go to last letter (one square) and remember the number of Adr. dec. in this case is 26431

previous to save new file go to first MODL chunk (in old file was the Third MODL chunk called Holster) and after word PRNT is called dummyroot_holster1 we must rename it to the bone this will be attached in this case bone_l_thigh so only write on it, and will be appear letters we no need (lster1 in number is 6C 73 74 65 72 6C)

and that code into left windoe we must change them to 00 00 00 00 00 00 like this

make the same process into PRNT of the second MODL chunk called polymsh6 ready now save as MODL holster 26431.msh

B) STEP 2: Putting into our model
open the file MODL holster 26431.msh (our holster model) using XVI32 as always xD, select all (will appear all in red) and press CONTROL + C(copy) now in other XVI32 window open rep_inf_ep3trooper.msh and search the word bone_l_thigh search that word until you find the last appearing of word and put the cursor on the M of the next MODL chunk to it, (in this case called eff_l_calf) and been on the M press CONTROL + V (paste) so will past our holster model select previouly, now we must rezise encode number of HEDR & MSH2 so go to begin of the file where say HEDR and put the cursor into next letter to it and go to Tools --- Data Inspector pop up little windows so remember his Longint Number (170176)

without close the little window put the cursor on next letter to MSH2 (167124)

now yes close that little window and putting the cursor on next letter to HEDR go to Tools -- Encode Number and put this number:
Longint(170176) + Model Number(26431) + 2(becase was 2 MODL chunks, Holster and Polymsh6) = 196609 and press OK

now go to next letter to MSH2 and go to Tools -- Encode Number:
Longint(167124) + Model Number(26431) + 4(2 per each one MODL chunk and we added 2 MODL chunks Holster and polymsh6 and 2x2=4 lol) = 193559

ready now save as rep_inf_ep3commander.msh

C) STEP 3: Adding Texture for our MODL chunk into new model
open the file rep_inf_ep3commander.msh using XVI32, put the cursor on M of MATL and select until letter previous to M of the first MODL word like this

press CONTROL + X (cut) and open one new XVI32 window and paste it there, now into that new window with our MATL go to last letter and remember his Adr. dec.Number (243), now open other XVI32 window and on it open the file rep_addon_dc17holster_l.msh and copy since the M of MATD until previous letter to M of the first MODL word like this

and paste them on our extracted MATL after last letter like this

now we must resize our MATL because we added 2 MATDs, so in our modified MATL go to new last letter and remember his Adr. dec. Number (527) so go to next letter to MATL and go to Tools -- Encodenumber and put this number:
MATL Adr. dec.(527) - 7 (always 7, no reason) = 520 and press OK

and after encode number we must change MATD Quantity so after MATL word into numer left window appear the codes: 08 02 00 00 02 00 00 00 we must change it to 08 02 00 00 04 00 00 00 (we changed 02 to 04 because we added 2 MATDs) now ready select all (since M of MATL until last letter) and press CONTROL + C (copy ) and go to our file where cutted Matl remember? well put the cursor on the M of GMODL and press CONTROL + V (paste) like this

now we need resize HEDR & MSH2 you remember how no? so now jump put the cursor on next letter to HEDR encode number same as previous we made and put this number:
HEDR Longint(196609) - old MATL Adr. dec. (243 + 1) 244 + new MATL Adr. dec. (527 + 1) 528 = 196893
then put the cursor on next letter to MSH2 encode number same as previous we made and put this number:
MSH2 Longint(193559) - old MATL Adr. dec. (243 + 2) 245 + new MATL Adr. dec. (527 + 2) 529 = 193843
now save as rep_inf_ep3commander_ready.msh.
open that new file using XVI32 as always and search the MODL chunk called Holster and after you will find the MATI word and after that appear the next numbers on left window: 04 00 00 00 00 00 00 00 50 change it to 04 00 00 00 02 00 00 00 50 ready now go to search the MODL called polymsh6 and make the same but in this case change 04 00 00 00 01 00 00 00 50 to 04 00 00 00 03 00 00 00 50 save changes because:
ALL DONE MAN!!

NOTE: little exaplain into last part of MATIs
MATL
MATD 0 ---
MATD 1 rep_inf_ep3trooper.tga
MATD 2 rep_addon_dc17holster.tga
MATD 3 weap_inf_dc17pistol.tga

for this reason into Holster MATI i said 02 and into polymsh6 MATI i said 03



please my english is bad so if something is wrong explained or confuse please post comments suggestion

CREDITS:
* B.I.G_Cookie
* Darth_Spiderpig
* Delta-1035
* Fiodis
* ThePanda
* RepSharpShooter