Yeah, I sometimes use a HUD, but even then, there are a lot of stats you can work out based purely on the board and your hole cards.
I've focused on outs and equity, generally, and figured that I can usually tell if something has a favorable equity or not based on the outs I have, and the past play of the other players. Fold equity has been the most important aspect for me so far. It's amazing how many
hands you can win without a showdown!
I'm pretty happy that I started taking the MATH more seriously lol