Repairing and Painting Pine Doors

[CptHastings]

I have moved into a house that has reclaimed pine doors that are in a poor state of repair ( large gaps in beading around panels,open joints,previous handle holes etc) I have decided to fill in the gaps and paint the doors. Would it be ok to fill gaps with decorators caulk or should it be wood filler? When it comes to painting should I use Primer then Undercoat before the Gloss or can you buy a product which does the combined job of the Primer/Undercoat? Thanks in advance.

[CptHastings]

The property is very old and the doors are all shapes and sizes. Few are of standard size and it would be necessary and very costly to have them custom made.

[buildersmate]

Decorators' caulk works best on narrow gaps that are subject to slight movement because it flexes a bit with movement. Being supplied in a tube it is also quicker to apply. Wood filler is better if you are matching the colour of the wood because you want to coat in polyurethane or similar, where the wood grains show through. You can fill bigger holes with wood filler (though more than one application may be necessary).
For what you are doing (painting the doors afterwards), I'd use whatever is easier - which may be a combination of both.
The best finish is always obtained by several thin coats and light rubbing down between. But it depends how fussy you are. You are clearly hoping to get away with only 2 coats of finish in total. Since you are saving money by re-using the doors, depending on the value you place upon yout time, perhaps best to consider 3 coats anyway. The first one being a decent primer.

[heathfield]

I've had the same problem in various properties I've lived in. I found early on that Polyfilla is ideal. It's quick, easy, and lasting, and Ive used it successfully to fill not only big dents and scratches, but also large holes where locks have been removed. Caulk tends to have a flexibility that you wouldn't want. Use a primer as a first coat to seal the Polyfilla.