With things like hot glue and really super glue, you actually can't fuse the joints together so they'd "break apart" easily enough and you could try cleaning them out and whatnot. Only certain materials actually fuse plastics together, especially the polyvinyl figures are made out of these days (generally).
The problem with the vasoline idea is it can mix with the hot glue... Making the hot glue essentially not stick to much of anything. Hot glue's a weird thing... It's kind of actually similar to heating plastic and injecting it, ala the production of figures. I've actually injected hot glue into molds and come out with a cast that wasn't too bad.
It's of course a poor material to cast with though but not bad for prototyping.
Anyway, mixing the vaseline with the glue can ruin the overall effort, just a word of warning.