For your first question, it really depends! You'd have to edit the textures to match the coloring of the avatar you're fitting it to, as well as scaling it to where the correct position is that you desire.
For your second question, most use what's called "SPS" now by the creator "Wholesome" on Gumroad. Completely free, even with tutorial videos for easy use. Old ones tend to use what's called "DPS" but it's no longer updated for some reason.
