Car paint that seems to melt?

[RazerSauber]

Hi guys. I've started the process of respraying a bonnet on an R50 Mini and I'm having terrible trouble with the paint. there's obvious evidence that this has been painted before (By a chimp I suspect. Over spray in places I didn't think you could get it) and the paint is awful. It's in a "near enough" shade of liquid yellow that has some deep cracks in. Cracks are a good .5mm deep and wide enough to fit a ball point pen in. I set about the cracks in the paint work with a mouse sander and after about an hour had managed to smudge some of them but as I'm sanding the paint sort of melts? There's no lacquer involved here as far as I can tell you, just paint. It clogs up sand paper at a rate of knots and even sticks well to the pant/rust removal disk I've got on my angle grinder. Is there a faster way to get rid of paint like this? I don't want to go out and get paint stripper as I'm meant to be doing this job on a budget (the intention was a rattle can finish and the loaning of a polisher) and I preferably don't want to spend all the hours god sends taking the whole bonnet top back to bare metal. Is there anything I can do to the paint to stop it 'melting'? I can get some pictures if it'll help with the description.