Well I think this is like driving in the real world. I don't watch my speedometer when driving f.ex. in a city. I can pretty much use my senses to decide how fast I can take a corner, altough I'm not usually racing while driving in city. If I was, I could imagine that I don't have any time to watch speedometer, nor the need.

The way I memorize track is by going quite slowly, trying to memorize the driving lines. After that I put up some speed and gears if necessary and start memorizing braking points. After a while I know HOW MANY GEARS I TAKE DOWN before turning to hit the apex. When you get to the right gear, you can quite easily speed up or brake down easily without spinning in the corner.

So by determining how many gears I have to take down and approximately slowing down so much that I don't rev the engine and I can do any curve quite decently.