It really does depend on experience, conditions, tyres and wot bike you're riding.
I tend to use the rear quite a bit at slow speeds when scrubbing off a few mph for example but less at higher speeds. For 'proper' braking nearly always front wet or dry with a tiny bit of rear if needed.
Does depend on which bike I'm on though, my Gixer 11 rear brake is so poor and tyre so grippy then a decent boot doesn't do that much and when your have to stomp then not much feel ;D
On the MT03 the rear is better but I do get the odd lock up from down changes anyway, particularly when 'making progress' on wet, slippery backroads.
I've got a few other bikes of various ages and various tyre/brake combinations and it always take a few miles to get the feel back for each.
As many others have said, get some training, find your preference then practice, practice, practice.
If you get a chance off road riding will really help. Hasn't got to be 'proper' green laning stuff, I learnt a lot as a kid on a ratty step thru in a large grassy field, come to think of it learnt quite a bit as a kid in grassy fields