Ah, my sympathies, I had massive oversupply and had many issues with mastitis and blocked ducts. Have you read about block feeding? It’s basically only feeding off one side til it is empty. It is uncomfortable and you feel scared about getting too engorged on the other side, but really it’s the engorgement that is sending the signal to your body to produce less, as it’s being unused.
With oversupply you need to be careful not to additionally stimulate your breasts with expressing, even sometimes the hot water in the shower made me spontaneously produce loads and I had to try to direct the water away from my boobs.
Im not sure if this is accurate, but I always felt that if there was a reduction in frequency of feeds that was consistent, it usually took my body 3-4 days to get the message. So hang in there with engorgement during that time and it should improve.
That said, if you get signs of blocked ducts or mastitis, you need to take action to clear the block, which is counter to the advice above. Warm wet heat, massage and expressing out from the sore area. Although a poster recently told me they no longer recommend heat - possibly because of the issues above - was the only thing that cleared blockages for me though.