I started using liquid clear but I am much happier using linseed or safflower oil. Linseed is a bit yellow vs safflower. If you pull the material safety sheet for liquid clear its a mix of the two plus some thinner. The problem I've had with LQ is if you get even just a bit thick, your pigment will sliiiiiiiiid down the canvas before it dries. Also, getting thinner on it is bad.. very bad. What I do now is if I need the whole canvas covered, I'll use LQ because I have it but I put in on then use a shop paper towel to wipe it down so it's a THIN layer. Thinner than liquid white. And I am extremely cautious with making sure my dry is dry and little thinner gets on the painting. Or I use linseed oil.. very thin coat. I love working with black canvas ( black gesso) so I'm always experimenting with things.
PS - what happens you ask when you hit LQ with paint thinned with thinner? Oh.. fun stuff. .I was working on a space picture with stars so I thinned out some Ti White with some thinner and flicked it on the canvas.. each flick ended up with a "halo" around it as the thinner reacted to the LQ. I ended up brushing out the stars.. then thinning some TiWhite with linseed oil and flick, flick.. that worked pretty well. No halos.