I've tried it (thanks Bill Kroen!). It works well. I've used both a regular club and my homemade momentus - much harder with the momentus!

But as you say - you can feel different things and correct them. Your brain (when practicing this way) isn't focused on speed, but rather the feel of the positions. So to move this way, you impart the feel of good positions into your brain. Then you speed it up, hitting those good positions. Then you hit the ball well, and play good golf.