3x3 with feet
Parts of the feet to use
Basically you want to try to use your big toe to turn each individual layer needed while trying to hold down the other two layers with your other foot. By knowing how much pressure is needed to hold down the other two layers with your other foot, it will take practice.
Also you could try to turn the top layer of the cube with your big toe while holding the bottom two layers with your other foot. It might work for you or not.
Try to solve the cube with the least amount of moves, so I would suggest using the Petrus Method or another method that uses the least amount of moves.