Robs Papering & Painting

Check there are leaks around the seams or valves of the radiator.
radiators need to be thoroughly sanded down or treated with the paint remover as left over paint will probably bubble if just overpainted with enamel paint.
use a radiator paint primer and ensure the coating is not stepped or overloaded with too much primer.
best finish for a radiator is to use radiator spray canisters available from most diy stores such as wickes, and b&q.soray in a smooth regular action 6-8 inches away from the radiator.avoid hand brushing as this creates unsightly tramlines on the radiator, and irregular thickness of paint on the radiators angled metal structure.

Best option is to paint the door frames first.,a few days before the doors are being fitted.
avoids the risk of contamination of paint onto the oak finish of the door faces and edges.
any damage to the paint as a result of fitting the doors can be simply rectified with small paint repairs /filling later on.

best to use a ready mixed paste which can be used as a paste the wall technique.
if walls are subject to a lot of small cracks then erfurt recommended cohesive may help to give a smoother adhesive finish behind the lining paper.
i have used solvite extra strong however, and found it to be fine

Remove flaking paint using a wire brush and ensure all dirt is removed.
use an external damp seal paint as the gable end of a house is subject to a lot of wind and rain and needs additional protection.
sand down any paint craters prior to applying external paint.

Using frog tape involves a lot of expense and time having to place and remove and then replace and remove again if having to apply 2 coats.
i personally do a lot of cutting in work without tape, except for areas such as bottom of skirting boards, where a certain level of protection should be given to hard floors and carpets.
there can be a misalignment issue on frog tape using it in the same area twice for two coats, so i tend to use painters tape which is lower adhesion, and cheaper.