Pin prick sized holes in gloss of painted wooden window sills

The problem you have is called ''cissing''. It's usually caused by a chemical in furniture polish. The previous owners have more than likely polished the sills in the past. I would recommend re-sanding, use an oil based undercoat and then gloss on top of that. Also try and avoid 1 coat glosses where possible, they aren't that great. Hope this helps.

Pin prick holes tend to be the small holes in the grain which have opened up when stripping. Bare wood going to white gloss should ultimately have 4 coats of paint, 1 x primer (which seals the wood) 2x undercoats to bring the cill up to a solid white base, then a gloss as a finish coat. When painting, I wouldn't use one coat systems, especially on bare wood. You should always use the undercoat to blanket the area so there are no misses or patchiness and the gloss is only used as a finish (not necessarily to try and cover previous coats). If holes are still there, it's recommended to use a fine surface filler after the first undercoat. Once dry and sanded, a second undercoat can be applied. That all said and done, if cessing has been ruled out, cessing occurs when there is a reaction with paint where there is a barrier between paint and the surface ie grease, resin, even every day dirt. It's always best to wash down with with something to neutralise the wood especially after using sugar soap which is a chemical. I personally use a white vinegar but paint stockists have various products that can be used to neutralise the surface.