Finalization takes so long coz it does BRUTE FORCE. Brute force is process of trying to find the password/code by trying all possible combinations. It can take many hours. You can use FAR MANAGER and try not to use brute force and save your time. I don't know if this can work for your phone. MAIN and FS are just copied to the phone... No brute force used here.
I use Phone XS to upload FS then FAR to finalize phone and then upload MAIN with XS++. :-D
Greets