JoeJoe wrote:
What is the difference between a primer and an undercoat?
Looking to paint doors, skirting, and facings - all are now striped.

You're supposed to paint it on all over in one coat, not stripe it!

Primer is supposed to "stick" well to the timber (or whatever).

Undercoat covers and is very opaque.

Gloss is the final thin "shine".

I wouldn't buy cheap paint.