How would stain blocking shellac work on latex primer?

Sure you can. A shellac based primer would work over latex primer with no problem.

Hi Heather! It would work just fine.

What project are you working on? Furniture? Floor? Why do you think you need more primer or shellac?

When you use primer it does not normally look like a coat or two of paint-- or in other words--you can still see what you are trying to hide. It may seem like it's not covering what you are trying to hide--but in reality it's doing it's job. It provides adhesion for paint and gives the paint more durability.

As above primer is preparing the surfacem giving the adhesion you need, to enable to paint straight over it.Using the best quality primer is the key, Zinsser bullseye 1-2-3 primer I use for everything and gives a brilliant result every time. Good luck with your project.

Stain blocking primer is used to block stains. So if you're painting a mahogany piece white and the tannins bleed through to show pink spots, that's what you use.

To go white easier, use a cheaper primer like Zinsser 123 or spray it with white spray paint even. I like to prime my pieces and then use white latex in eggshell. Something about the eggshell finish covers better.