Depends on what you're doing. Monster mud adds some thickness to the prop given it some stability and longevity. Just using paint will keep it flexible so when you move it, you have a greater risk peeling, flaking and cracking the paint.
If you have a harbour freight near you you can buy a mixer adapter for a drill for as low as $4 HD have them for 5 and up.
But in the end experiment with it and see if it works for what your goal is. There are no hard fast rules except "use what works, toss what don't" oh and Have fun with it.