How to support bf

I (23F) have been with my boyfriend (26M) for four years and while I love all things associated with male anal sex my bf isn’t a fan. I have put my finger in his ass a few times but he didn’t like it.

We unexpectedly found ourselves alone on Christmas night and decided to have some drinks and sex. He started by telling by me that he thinks we should start saying yes to more things sexually. When I asked him for examples he said that if we arranged a threesome he would like to suck the guys cock. Later on he then admitted that he has been fantasising for a while about fucking another man.

Whilst I was giving him a blow job today he asked me to put my finger in his ass. He was moaning on my finger and stared grinding on to it.

I just want some advice on how to support him while he explores this side of his sexuality. Also, any tips for playing with his hole are welcome.

Thanks for reading this far!