In my experience i try to go faster on a downhill which puts me a little ahead of the pedal

i imagine the top of my chain being loose (backpedaling/coasting) vs taught (pushing)

i try to pedal in such a way that would keep the chain tight thruought the whole pedalstroke and it seems to work out for me

just work on your form on a pedalstroke at all speeds and it should all fall into place