These are the stages necessary to decorate new woodwork:
1) Give it all a quick sand with 80 grade paper to remove all the worst rough edges. Also sand all of the 90 degree angles because paint will not hold to them.
2) Apply knotting solution to all knots, preferably 2 coats. it dries in 20 minutes so can be done pretty quickly.
3) Fill all larger holes (ie screw holes) using a 2 part filler – known in the business as 2-pac. After 30 minutes this can be sanded flat.
4) All of the smaller holes (nail holes) can be filled with any ordinary filler. These can be sanded after 2 hours or so.
4) Apply 1 coat of high quality water based primer. Probably the best stuff to use is the Blue Zinsser primer.
5) Caulk all gaps (top of skirting boards , check for any further sanding required. Reprime any remaining bare wood.
6) Apply 2 coats of your finishing coat. If you are glossing apply an oil based undercoat first.