Nice work! The best videos I’ve found on blackberries are from a farm in Alabama. They have a YouTube called Petals From the Past.
I’ll link an old trellising video but they have an updated multipart series that is really well explained in case you were curious about how to get good production with less of a tangle. Hope this is helpful for you, it has definitely helped with pruning mine and clients’ blackberries
https://m.youtube.com/watch?v=X2-reKF7XVI&pp=ygUhUGV0YWxzIGZyb20gdGhlIHBhc3QgYmxhY2tiZXJyaWVz
