Would any of the methods above work for a tiny dimple on the gas thank? It's probably about 3/16" round, if that. It really bugs me...
the type of kit mentioned by bicycleman is ideal for pulling out small dings like yours, without damaging the paint.
if you're lucky it will pop out in one go and barely leave a ripple behind.
i've done a few like that myself with £10 kit off ebay, works with glue sticks and a threaded bar pulling against an inverted cup.
if it does leave a ripple that's visible in sunlight, a light sanding with fine wet& dry followed by a good t-cutting can fix it up.
managed to pop a dent once using the mirror stem through the filler hole in the tank, barely visible and didn't crack the paint.
another time i put banding straps around the tank, trapped a plastic bag under the filler cap to block off the vents, then attached a footpump to the fuel tap and pumped it up. - that was on a tank with more than one fist sized dents that needed respraying, but i didn't want to lose fuel capacity by just filling the holes - it worked great but the tank was a bit bigger than standard once i'd finished!!
here's a vid of how the pros do it with an expensive 'proper' pdr kit... http://www.monkeysee.com/play/11977-...epair-with-kit
also below some other methods, including dry ice, which i can say i haven't heard of before, though i have seen dents popped successfully with plumber's pipe freezing aerosols
they mention the 'rivet' method for large dents - ive used self tapping screws before, obviously not on fuel tanks! and this works great, leaves you just a little hole to fill.