Everyone is different. I work on it all at once focusing on one step at a time. The first focus is basic strategy. Then when you have that down counting. After that indices. I find after a long enough time working on 1 thing my productivity goes down so at that point in the drilling I would work on something different until my brain is ready to go back to the primary task at full productivity. Now you mentioned working on two things at once seemed to be counterproductive but you were trying to play the game without having all the pieces down cold. You learn everything independently first and then try to use them together. Try learning counting by counting down a deck of cards 1 at a time then when that is pretty easy do it in groups of two cards and three cards etc. At a table you will be using card cancellation to accelerate your processing. You might look down and see 5 non-neutral cards. 2 high and 2 low cards cancel out leaving 1 card to count so instead of counting 5 cards you cancelled 4 and counted 1.