For various reasons I can't use an edge strip on some tiling I need to
do, so will finish the edge with a small fillet of grout (or maybe
silicone). The tiles are white but the glaze doesn't (as usual) cover
the whole of the edge. They're also thicker than usual. To stop any
of the brown unglazed edge showing through, I thought I might paint
the edge before sticking them up.

Question is, what's the best way to paint it? Clearly, 'tile paint'
is only designed to cover the glazed surface. Would a regular primer,
undercoat, gloss approach work (which might give the best outcome) or
would it be better to use emulsion? Maybe seal with some PVA first?
I have a vision of the tile sucking most of the water from any paint
pretty quickly...

Cheers