Adding Minor Textures?

So I have a character that alrdy has color textures. No UVs at all for him since he is a toony creature. I want to give him like paint splatters or something in an animation, but I don’t know where to start. Should I create a UV of the extra colors and map it onto him with alpha? If so, how would I do this? I can model and put in colors, but texturing isn’t my strongest point.

Thanks for any help!

Yes, that is how I would do it. If you don’t want to do a lot of unwrapping just for one or two spots, just load the whole thing, with all faces selected, then move/scale them in the UV editor, so they are completely in the alpha area of your image, then, re-unwrap just those bits that will have splats, using the ‘project from view’ option, and scale/move those UVs over the splats.