I would rather rub my cock around the hole as a way of asking.
I agree but there are also people who would like that, and perhaps not much more. Some people are into finger play but I think that it can have limited merit/appeal. (Keep your fingernails very tidy).
I usually follow it up with working on increasing the intensity of physical intimacy, perhaps through more kissing, ear nibbling or flirty eye contact.
[Hmmmmm. Thinking about what seems to happen naturally, and trying to record it so that it makes sense...]
I think, usually with my cock closely in position, I ask (whispering quietly --lol, well, my sexiest quiet whisper--- and tentatively into the other person's ear "would you... (pause) like a little bit more? (add: ear nibble/kiss/intense eye contact/little smile)".
If the answer is affirmative I might ask as some stage "would you like a little or a lot" (still quietly/whispering), and check as things progress that things are feeling ok.
In my view anal sex is special because it is very intimate, and you do need to ensure that there is a lot of intimate, and reassuring (respectful but still sexy) communication.
I've been used as a human dildo often enough in the past. It might even be casual/recreational sex, but no one (well some exceptions
here immediately come to mind) likes to be treated as
only an object for fucking.
I have posted about anal sex, technique, and intimacy before but I think it is worth making the additional points above. People seems to appreciate a few pointers from time to time.