Not sure if you are talking about store-bought or homemade. I made mine and painted it with two coats of gray Dry-loc and then detail painted with exterior house paint. If you are talking about store-bought, I've heard that you can buy exterior clear coat paint (varnish?).
Is it necessary to protect them? I've never done it myself. So far, all I've used is the beaded white styrofoam. Just paint. They get left out for a few weeks before Halloween and a bit of rain in the mix, but I haven't had any issues.
I guess it'd depend on what yours are made out of.
My stones are all made from 2" rigid foam (pink and/or blue). A good coat of exterior latex paint is all I've ever put on them and they hold up fine for years. I just did a few minor touch-ups for the first time on my oldest ones last year and they were made back in '99.
I have a decent sized platoon of skeletons. Some are several years old which means there are cracks and breaks in the plastic. What is the best way to fix these guys?
For example (I wish I had pics) one's neck is broken almost to the point of decapitation. Another's foot came off - it was...
I made this prop about 10 years ago and I no longer have use for it. It needs a little TLC, some new paint and some labels I had printed have fallen off. It has lights underneath the foam that still work.
I figured I'd take a shot to see if anyone on here wants it and lives close enough to come...