About a week ago I found a leather rounder on ebay and managed to get a great deal on it! I’ve used it already a couple of times, once on the rawhide hobbles and once for a keychain.
Basically how this works is you put the braid into one of the holes and pull it back and forth and it forms it to a round shape and polishes it up a bit. I wouldn’t use this on a bullwhip because the braid will need to taper and I don’t think you’ll get as good results as board rolling…but on plaited items with no taper it will work great!
Here’s a key fob I made with some of the scrap from my 20 plait whip: