mbm, in answer to your question in the earlier post (I had to go do pony chores) ….
Relative to actually ponying the foal, …. that is more dependent on how nervous your mare is about outside threats. Your mare needs to be able to ‘come back to you’ (listen and oblige) quickly no matter what the distraction, so when you feel comfortable that she will trust you over ‘possible’ threats to her foal would be when it’s ok to pony the foal.
I would start on the ground with the foal using a 1" 100% cotton rope as your lead line or your groundwork line(s).
I cannot stress enough … 1" 100% cotton …
I have several in different lengths and with various hardware depending on what I plan on using them for (25’ for trailer loading, 10’ and 12’ for leading, 15’ to 25’ for some ground work, etc.). I ended up making my own (order it by the foot) and I know how to splice (some ropes splice more easily than others and I hate doing it). If you need help with splicing try a good western saddle shop, cowboy, horseman, sailor, or boyscout.
I use brass bullsnaps for some of these ropes, or use a stainless or brass ring and have a stout leather strap with a buckle that attaches to the ring and you can buckle onto the halter ring (that is the absolute best way to go for safety).
And I also like to replace the halter crownpiece with one that is wide and padded.
While it is a pain to organize all of this gear, it is something that you will be using for a while. The 1” cotton will not burn you, your mare or your foal, especially around the legs.
You can do a lot with ropes.
Once you get ready to pony, don’t ever tie anything to your horse, ride with the lead rope under your upper thigh and hold it in the opposite hand along with your rein. You can let it slide a bit and you can shorten it up, easily.
Or you can just lay it over your thigh but you will have less control that way.