This comes up more often than you would think, and it's so simple.
First, set aside 6-weeks, no not joking.
The colonel has laid this out here numerous times; thanks a bunch L!
Search his recommendations for the "AIP"; it's on-line now, free and searchable. Download it dummy (PDF).
Search his sections, print them, wright them out (

), sleep with them, make love to them...
Then, you mentioned Aerocourse. They are up-to-date, leaning on the NEW, verses the OLD. Run it, make love to it, many times...and repeat.
6-weeks, that'll get you a pass. If you want above and beyond, then engrain the ADF/NDB shite of old. Be able to plot time and distance to station via crossing bearings, and know cold, how to find your position via relative bearing, track, and station...running two fixed, or two RMIs, or one of each. Know it cold, and that will get you into the 80s.
You want 90s, it's 6-months and a tutor out of one of the colleges...
How is this hard to understand?
"Long is the way, and hard, that out of hell leads up to the light".
http://www.youtube.com/watch?v=XM3lDvhRzsQ