I use a mono backer, usually whatever I have laying around. I look at the reel's IPT and the spool capacity for the closest line size to the braid and kind of guestimate how much backing to put on and how much braid to put on. So say your reel does 32inches per turn (I know this isn't quite accurate as the spool will pull in more/less line when the spool is full) and at 10lb mono it'll hold 150 yards (450ft). So roughly 3 ft, per reel handle spin. I typically only put about 75 yards of braid on so if I put on 40lb braid (which is 10lb mono equivalent) I'm only going to turn the handle 75 times after the backing is on (or close). So same with the backing, I want to put whatever the spool capacity - 75 yards. In this case, it's also 75 yards of mono.
I hope that made sense. I've used 10-15lb braid on my finesse setups, 20-40lb braid for my jigs and t-rigs and for frogs, I've used 50-65lb braid. This year has been an experiment for me because I started using fluoro a little bit more. Braid was nice because it lasted so long, but I've noticed a higher number of bites on fluoro.
As for knots on braid, if you power pro super slick, I've had the improved clinch slip. Couple of things you can do is try to take the coating off the last foot or so of the super slick by running it inbetween your finger and your thumbnail or you can use the san diego jam knot or the palomar knot. On regular power pro the improved clinch works fine just leave a little longer tag.
Good luck.