Repair the cracks and holes in the wood with a wood filler. Brush knotting compound over any knots to seal in the resin on bare wood. It's also worth washing old paintwork with soapy water or sugar soap to clean away any and dirt or residue
Use a scrapper to remove flaking paint and sand it smooth. Seal any bare wood with a quick-drying wood primer. Work the brush well into any mouldings but don't overload the brush or the paint will form drips on the surface.Then leave to dry.
Apply 2 good coats of undercoat . Then,when dry apply the topcoat. Try to use only the top third of the brush and start with smooth vertical stokes. Brush the paint out & finish off with light brush strokes in the direction of the grain.