If you can find someone else to practice with (another student perhaps?), doing it over Skype is a good way. Plan a route in advance which involves different services at airfields (ATC/FI/AG) and passing through bits of airspace/MATZ.
One of you acts as the controller and away you go, with the "controller" perhaps telling you someone has reported seeing smoke from your engine (cue a Mayday), asking for position reports, perhaps trying to catch you out by not giving you a zone/landing clearance or forcing a divert. They give you feedback and then you get to return the favour.
Through doing this I passed my FRTOL practical last week first time, despite being little more than glider ballast without so much as a bronze to my name, and very little "real" radio practice (calling downwind and asking the FISO to enter the runway in a buggy just about covers it).
I attended a day's groundschool run by the examiner before taking the written, then after that relied on CAP413 and some of the notes on
http://www.dustableradio.co.uk (although there are a few inconsistencies, I was told to take CAP413 as gospel). Personally I didn't need any other book, everything is in CAP413, although it is quite long and has some sections that can be ignored for the test.
Having done the written test, someone already with an FRTOL acted as controller/mentor for three of us (at once!) for four sessions, then I did about another four practice sessions with another student (who also passed comfortably). We also had a mock over Skype with the examiner, which we got feedback from, before the real thing, so to be fair they were very supportive.