BPF. Fully support the flow approach which develops that important muscle memory and works well for pretty much all of the GA aircraft.
As for teaching it, the formal lesson is just that. I'm of the view that I'm introducing elements of the (P)FL from effect of controls (mixture, throttle, carb heat) onwards. FREDA has the fuel calculation and tank swap (where appropriate) element and when estimating the effects of wind on track and groundspeed I usually make a point of showing it in the glide as well as with power. All that builds towards the formal PFL teaching. After the formal lesson, my students can expect a PFL at any time and from any altitude on the transit to or from the training area right up until their skills test.