CBT and DAS encouraged the same thing for me. Slow speed manoeuvres, use the rear brake. The more that I have been riding though, the less I have been using the rear, slow speed or not. I tend to only use it now for hill starts occasionally, and with the front in emergency braking.
under 15mph think I got told when doing lessons, my comments are more towards over cooking it into corners thinking your back brake is helping u when in fact it might be hindering u. especially in panic situations, I've no feeling though the foot with boots on, if I was tracking I would get a thumb brake and try trail braking where I feel it would be beneficial, im not being smart but if your flying past me trail braking into corners on the road your one brave person, because my bottle is starting to go, a bit
I find that if I am a bit hot in a corner if I roll off the throttle it will pull the bike into the corner without upsetting the suspension, helps it drop in , sort the corner before you get there that's the secret,
Rear brake is beneficial in many situations, both road and track. In all cases though it is used lightly and I have never felt the need to have more stopping power from it. I have actually thought about introducing some air into the rear system to make it softer and less responsive. However that would make it inconsistent so may not be the best idea after all.