Is your plaster fresh as in dried for a few months or fresh as in just changed colour? Only you should be allowing it to dry thoroughly.
I would put the skirting on after the mist coat and fix the top edge with sealant/prime the skirting, but it doesn't take me long to cut the paint in on the walls.
If you get the rads sorted/dry the walls you can always paint behind the rads as far as you can see with a roller on a long arm.
Is your plaster fresh as in dried for a few months or fresh as in just changed colour? Only you should be allowing it to dry thoroughly.
I would put the skirting on after the mist coat and fix the top edge with sealant/prime the skirting, but it doesn't take me long to cut the paint in on the walls.
If you get the rads sorted/dry the walls you can always paint behind the rads as far as you can see with a roller on a long arm.