I did 7 subjects in 8 weeks self study while doing a Nav a day also for my CPL.
You'll piss it in with Bob Tait, allow 2 weeks for performance and get as much info on echo as you can, I taught myself how to do it by working from the answers back, cross referencing the Bob Tait and ATC texts for that subject.
It will also be good practice for your ATPL's
GG