Im struggling to figure out how to go about coming up with different frequencies preflop (and postflop). I sort of just estimated my ranges so far in different situations based on personal experience and all the studying ive done up to this point (watching videos, reading books, some self study, etc). However, im trying to be more concrete about why im opening a certain frequency and how factors like the size of my open raise, and position should affect that frequency. I sort of thought the min defense frequency would be useful for figuring out frequencies for defending preflop in headsup situations and especially in post flop situations. However, on one of Sauces videos couple months ago he replied to me saying that MDF is not a good way to think of preflop because if were not 3betting our entire defending range then villains hand always has EV when called. So, im confused how to go about coming up with frequencies preflop. And also just how useful the MDF is for analyzing defending frequencies on the flop and on the turn, since the only part of the hand that i know MDF to be really useful is the river at the moment. Id buy coaching to figure this stuff out from someone knowledgable i just cant seem to find any answers anywhere.

Any help, opinions, whatever, is appreciated.