I use my knee lift with my right leg and my right foot for the foot pedal. It's just 'natural' to me, I guess. But then again, I drive a standard, a motorcylcle and boats so I am used to having lots of moving parts :-)
Maybe it is something you need more time with. Someone mentioned wrapping their knee lift with batting. Perhaps you could wad yours up to see if cutting down on travel times helps. I'm sure different body builds factor into the use of these things- I have what I refer to as a peasant body, tall and sturdy.
Good luck. Keep at it. I have a difficult time switching to my old Singer (70's Vintage) because she lacks the knee lift but going to the treadles is not an issue. Go figure.
best,
d