See, if you want to paint directly onto your 3D models then try ZBrush. it is quite expensive, mainly used for sculpting. It also have tools for polypainting which allows you to paint directly onto your 3D models. After polypainting your model in ZBrush, you can create UVs for your model by using UV Master Zbrush Addon. ZBrush is less memory intensive tool as compare to Maya or 3Ds Max unless if you are dealing with millions of polygons.
I am not familiar with 3D models but I've seen people using Maya or ZBrush.
I usually use "Unwrap UVW" and peel the model, and then use viewport canvas to roughly paint what the texture will look like. Then I move the image into Photoshop and edit it until it looks nice. The only problem I have is that it takes too much time, especially because Max tends to crash when I'm using viewport canvas, forcing me to repaint the model again.
