Correct, never learned to. I've always driven Showroom Stock/Improved Touring/Firehawk-type cars and just never learned the technique. Everything I've ever driven has been a syncro box. To manage engagement of the clutch, minimize shock on the drivetrain, and manage the forward weight transfer I tend to slip the clutch as needed (which I had to do a lot of at Summit Point last weekend through the chute...) but it's not a massive slip that's damaging to the clutch; ironically, my clutches tend to last a very long time.

Never learned to left foot brake, either.

Only time I found heal and toe to be very useful was in a Spec Miata. Really needed it for that to keep the car from swapping ends.