I have heard others talk about "loading up the roller" but, although I've only done small sections, I found that if I did that, I would lay it on too thick and get the texture you're talking about, and get runs.

The most recent time I tried it, I do load the roller up, then squeeze most of it out by rolling it hard through the tray a few times, then start on the painting, so long as the roller is completely colored with the paint. And I don't mind pushing down on the roller when painting the car either, it does leave bubbles but they go away quickly. The idea is to get the surface uniformly wet, even if really thin.

Your mixture sounds a bit thick to me, try thinning it more and that texture should go away since it will level even better. But then be extra weary about putting too much paint on, as it will run being thin if you put too much paint on there.