>>3565166I'm not sure who told you these things.
Cheap acrylic dries like a plastic and is super slick, it's hard to paint on. Gesso has just enough grit to it to hold the oil on the surface. Ideally, you go for three or four thin layers sanding between each layer for a pretty cohesive surface. You can get away with two, but don't just think you're smart and apply just one layer in thick brush strokes. If you're prepping your own surface, pay attention to the surface texture you're creating or you'll end up fighting it the entire time you're painting.
You can oil up a gessoed surface if you take a brush with linseed oil ona dry surface and apply it thinly, then buff off slightly with a rag. THis'll get the paint to slide across the surface, you can do the same with a toned wet ground (maybe 2 parts turp/mineral spirits one part oil is a good medium) and you'll have a wet ground you can slide paint around more easily in.
Generally, I triple-prime my wood surface, sanding between layers, make sure my drawing is pretty well thought out for any ambitious piece, then I seal the drawing with either shellac or an acrylic wash.
Acrylic washes can be great grounds, just let them dry first.
Mixing into any wet whites would be foolish though, everything will be too bright and too cool adn you'll end up with a chalky painting. And don't gesso a canvas with gouache, it's way too expensive and it'll reactive with water vs. seal like a gesso.
Good luck
