I have, and it works great. I may not be doing it the same way you do, but I'll bet it's similar. I take my 25ft soft cotton long line and slip the end through the noseband of the halter, then down between the front legs, then up and over the withers and back down to be snapped to itself. This way, when you pull on the lead, you're not putting any real pressure on the halter, it's all around the girth area. If I need to, I can take the excess lead on the other end and loop it behind to use as a butt rope. I'll take a picture of it this afternoon and post it tomorrow.
That is different, in that what I've done doesn't involve the halter at all. I run a loop around the butt, a loop around the chest, and grab all of them together over the back of the foal like a suitcase handle. You can move them backward or forward that way, and then a helper can apply pressure on the halter with a different leadrope and you work as a team. If your line management is good, you can lead the foal alone with just the halter and a butt rope around the back.
I'm interested in seeing your pics of your way!