I have newly plastered walls in my dining room waiting to be painted. I need to replace the plastic light switches and plug sockets (I'm getting someone in to do this). Should I get the new bits fitted before painting - to avoid paint on the new things, or after painting - in case there might be any touching up to do?
Don't think it really matters.
I would have the new ones installed first in case the electrician damages your pristine paintwork. Then "mask" your new plugs before painting with masking tape.
I've never much success in masking off when painting. My window frames are a rainbow of colours... I think I'll have the new sockets fitted then unscrew them a bit to paint to the very edge of the plaster.
One way to do this neatly is to loosen the fittings slightly to be able to paint behind the switch/socket. Then tighten up when dry. No masking tape/no messy lines.
Bear in mind that different brands are slightly different sizes / have different radii on the corners. Hence preferable to change the electrics before the painting.
My favourite trick, Misky, is to remove the plate screws on all the sockets and switches. Pull the fittings as far from the wall as the cables will let you. Place a small plastic bag over the fittings and wrap the bag tight to the cables with tape.
Paint away, then have the electrician change the fittings.