The ATP (and ADX) test has such a vast amount of Q's they can draw from (like 1500) that I really just learned how to do each problem.
There are some short cuts for Wt and Bal on the Beech 1900 and the 727 that some guys might not see that can save time - but as far as memorizing stuff there is just to much they can throw at you.
The FEX test is easier than ATP ADX but the WT shifts and 727 stuff are all the same... so do all three at the same time is my advice.
No the Inst test that one is a blast - I think I did the test in 12 min. The long problems are very easily memorized. After you work them through legit - make a chart - aircraft types and destinations will tell you the answer.
Just my .02 that and $5 will get you a coffee.