I use Squadron putty on anything plastic, solder on brass, and wood filler on (oddly enough) wood. I've heard of folks using Bondo for large jobs. I cannot comment on the Krylon, other than to say I've not heard the best reviews of it.
Squadron putty works well--you can buy it at hobby stores, the green stuff. But it shrinks a lot when it dries, which is annoying--you have to keep re-applying it. BUt it's fast drying and easy to sand. Some people use bondo, the car body repair stuff. I've never tried it