M Team, The "Official Community Guide" has a nice tutorial on weapon making and importing.
It should be located in your "doc's" folder. (ocfpscguide.pdf)
Also, a member by Bootlicker made a lot of useful tutorials & video for modeling & texturing.
Here is a link to some of his work...
https://forum.thegamecreators.com/thread/178084
Software you can use is based on your knowledge on how to use it, easy ones are Fragmotion, Milkshape.
Blender is free, but with a steep learning curve.
best
My games never have bugs. They just develop random features..
Lots and lots of random features...