Be very careful and consider the results you will get if you use a paint and primer in one step. I have seen a lot of ads pushing this idea of one-coat painting, but that just plays to people’s idea that painting is a drag and this would be quick and easy. It’s actually easier and safer to go with the old method because if you get the wrong primer in your paint and primer in one, you will be starting all over when you think you are done!
Paints are for looks and to some extent protection, especially outdoors.
Primers are for sealing and giving porous surfaces a first ‘drink’ so they are paint-able (so the next coat will bond).
What is inside your Paint and Primer in One?
But some primers are designed to seal, and some to create a bonding surface. What kind of primer did your paint and primer in one come with? I would not know either.
You have to know what you are doing before you go shopping. If you have a paint and primer in one tinted to your color and now you are reading this and thinking that you may have made a mistake: yes, I’m sorry that paint cannot be returned.
If you get it wrong, you will not seal tannins, stains, or maybe oils that you should have sealed. These things bleed through latex paint: latex does not have any real sealing properties. Sorry ’bout that.
Honestly, in most cases, with the right tools and the right clean-up tools, one more coat is not that big of a deal for an average room. Now, if you are doing a warehouse sized room, yes, maybe it is going to be worth it, but please call the paint store representative, perhaps even the district rep if you are risking that much investment. Paint store managers study the chemistry of paint and are trustworthy sources. You can always write to me also or leave a comment below.
The whole ball game is what are the solids in the solution? It is the solids that wind up doing the job for you.
When NOT to Use Primer (and When You Must):
Stains: at least spot prime where they appear.
Drywall: yes, always, but only with drywall primer which is not nearly as intense as stain killers
New wood: if pine, you will need an oil primer. Other woods you may get by with water-based. Ask your a paint store manager: they know. I have written about other paint issues here.