[Christ]

RE- "Slicking" caulk:
Keep a spray bottle of water with you - once you've sealed the joint, spray the caulk with some water, then finger slick it. It won't stick to anything wet, so your finger won't get nearly as messy.

DON'T follow the 30% rule - you don't need to over fill the joint to properly seal it. If you don't know what this is, don't worry about it. If you were ever told that you have to over fill a joint to seal it, this only applies to joints more than 1" in width, where expansion is an issue. When the depth of the gap is more than 1/4", back fill the gap with either foam or wadded paper. This will prevent the caulk from getting too thick, causing it to not cure properly.

The properly filled joint will slick down almost flush, but slightly concave, if on a flat surface. If in an angle, the caulk line's edges will be visually uniform, and taper from the middle concavity to the surface material until the caulk line is nearly undetectable. There should not be a ridge between the surface of the caulk and the adhesion surface.

Slicking your sealants will provide up to 35% greater seal and longevity in your sealant material.

Go to Wally World, and get a set of Cake Spats. You'll never need to use your fingers again.

If that won't work, often times, flea markets will have professional caulking tools, including bulk guns and slick-sticks (spatulas). I have a 2 foot bulk gun, some Albion cone tips, and a full set (almost doubled, if I can find the others) of spats, because as a Mason Apprentice, I had to learn to caulk. Once you really get used to the job and your tools, you can do nearly 70 ft/min, and make it look good while you're doing it. I'm not that good yet, but I can caulk just about anything and make it look like it's supposed to be there.

RE - Painting caulk - just use Acrylic or Latex caulk. If you already have silicone installed, wipe it with vinegar before painting.

RE - Poly foam and spray paint: Water based paints won't melt the foam, not that it was an important piece or anything. Oil and solvent based paints will give the foam texture, and thinning the paint will help that effect. It's not the paint itself that melts the foam, but the solvents and petroleum based chemicals in the paint, including Xylene (Xylol) and Toluene, Mineral Spirits, and other chemical thinners.