I'm currently in the application process. You have to do some tests first. The first one is a B.A.R.B Test, which is basically, you have to answer qusetions quickly but accurately (you can do the mock test on their site, just go on the search bit and type in barb test). The second and third tests are the, Basic Numeracy and Basic Literacy Tests, which you prolly guessed what tests they are.
Now, I haven't done training with them yet but I spoke to an officer in Bridgend. He told me that its weekends and depending on what regiment or corps you're joining, a couple of hours on either Tuesday/Wednesday/Thursday. If you complete 13 weekends you go onto a "boot camp" if you will, for 15 days of basic training. Now, I think they may extend that as the government has funded the TA's more to improve the training and expand the TA's. He told me that in those 15days, it's basically doing most of what the regulars do, but cram it all into 15 days.
Oh yea, if you complete atleast 13 days you get a £500-600 tax-free cash bonus.
That's all the information I can give you at the moment. May help you or it may not. Best of luck.