The end result will look something like this:
Be aware that this won't work with all weapons like highly detailed or very colourful graphics, but for basic weapons it should be alright. Games where the hud or hands block too much of the weapon image can be problematic as well.
So enough stalling, here's the steps:
Spoiler:So you have your model rip, what I normally do is remove the background then put a black one behind it. Then I scale it down and remove the black. This usually leaves little background imperfections, unless the weapon is black, which means I use a dark grey background instead. When scaling, have the hand you want to use with the weapon near it, as a general reference on how big it should be.
Spoiler:The weapon might look like this, but don't worry. With a little editing the messy edges can be cleaned up. For artifacts sticking out, use the eraser. If there's a missing part of a weapon use a brush in a fitting colour and the burn/dodge tools to make it fit.
Spoiler:There, isn't that better? Now we can move on to fixing up the colours. The anti-aliasing can mess up the colours and smaller details a bit, so I usually like to remove them or fix them up a bit.
For example, the brown is a bit messy with the barrel of the gun. Select the area of the colour and remove it onto it's own layer. You can clean up the selection with SHIFT and ALT.
Spoiler:When each colour is on it's own layer, use Hue/Saturation and Brightness/Contrast to colourise them.
Spoiler:After this, put on some final touches with Burn/Dodge (lining out details and shapes, adding hi-lights to other stuff) and put some hands on it and you're done!
Hopefully this is helpful to some of you modders out there! I don't release mods featuring my model rips often, but I thought it would be worthwhile to make a tutorial on how I do them.
