I pulled out an old sample of an oil primed canvas that I had primed over a year ago. It used to be fun experimenting with different kinds of hand-prime and the surface is unmatched. I've also been using Fredrix Single Primed (SP) oil ground, which is also good stuff, but no where near as good as the ground I made myself. The other advantage to making my own ground is that I can color it any way that I like; the Fredrix is also toned a light gray which is nice.
I'm going to let this study dry and work more on it tomorrow. I'll probably go back to priming all of my own canvas with rabbit skin glue + Gamblin ground simply because the surface is beautiful. And it's also much more cost effective.