Messed up spraying need advice!

I think the best way to do this is to treat it like an actual autobody repair.

If I recall, TS paints are lacquers.  If that's the case, Find some place that sells Gunze Sangyo Mr. Color Thinner.  It's a styrene-safe lacquer thinner, so you can disolve the paint without hurting the plastic underneath.  I think even tamiya might make their own version, but I never used it, so I can't vouch for it.

Anyway, dip a q-tip in the thinner and slowlly thin out the build up.  Feather it into the surrounding paintwork and then respray another light coat of paint, to bring it all together.

-Fred

More input please?

If you aren't keen on the patch repair job, you could always strip the whole thing & try again. You could put the model in a container / bag & fill with brake fluid, which will remove the paint - only issue is I don't know what sage of build the part concerned is in, if it well made up & has interior painting or what not done then this method probably won't suit, as it will strip everything.

When painting, build up light coats & then hit it with one last heavier coat to get a glossy finish.

#600 or #400 sandpaper.  400 does it fast, 600 may be better if you are not experienced at this.  Use wet or dry paper, bought at auto parts stores.  Some hardware stores have an okay selection of fine W or D papers, others do not.  This happens a lot, it is the big time consumer in model car building.