-What's the best solvent to use for cleaning up Plasti Dip?
Naptha. Or PD thinner, available a the same places as the PD online. Best thing is to not mess it up though, as it is a bitch to clean up if you get it in fabric. If you get it on a hard surface though, you can just wait for it to dry before peeling it up.
-Can we get recommended types of Krylon and Rustoleum? I'm tempted to pull the whole spray paint section unless we have a name for what's good.
the names for what's good. Both normal Krylon and Rustoleum paints are flexible when dry and formulated for use on plastic. In the end though, spray paint is an inferior weapon paint to a good acrylic.
-Are there any alternatives to Plasti Dip (aka why Plasti-Dip over others?)
Plastidip is really one of those products that is truly one of a kind. The closest thing is pre-vulcanized slush latex, which is a bit more finicky to apply, not as tough, and requires much more care. It's also harder to get a hold of, while you can get PD at home improvement stores. It also hits a bit harder than PD (it isn't quite as flexible). PD is also easily painted, while paints will peal off of latex over time without an additive. PD is also its own sealant and I am not aware of any allergies to its ingredients; neither can be said for slush latex.
So, basically, while slush latex will always be a bit of a niche product in weapons making, PD is just better in every aspect that I can think of.