I've been mulling this over and am planning on an overhaul to the purchase flow for next season. Instead of taking the user directly to the cart when they click "Add to cart", I'm going to prompt them to fill out the required fields (including assigning a curler profile). Once done there will be an intermediary screen asking if they want to add more items or continue to the cart. When assigning a curler profile for the 2nd, 3rd, 4th, etc. items the system will assume they are using the same one as earlier, but with an option to change it (to another existing one or by creating a new one).
I think this will achieve (A) a more straightforward multiple item purchases and (B) more streamlined curler assignment. It will overall feel more "wizard" like (if you know what I mean). A step by step, here's what's next approach.
Our data shows that most curlers only purchase one item in a checkout. But this is at least partially due to some of them not being aware that they can add more than one thing to the cart, thus creating multiple checkouts. Explicitly asking them as outline above should improve this.
This should also reduce curler profile duplicates. At least those on the same account that were created out of confusion.