I have done it at SFO (granted, this was in the summer of 2021, so may be different now). At Terminal 3 door 11 (as indicated on the link above), there is a booth with a person whose only job is dispatching wheelchairs. Have your wheelchair passenger find a seat nearby and go up to that booth and let them know you are there. While you are waiting, you can check bags if necessary and there's a restroom right there. If you can't check bags without the assistance of the wheelchair attendant, you can also do that after. It took us about 15 minutes until someone showed up, and it was fairly efficient from there. Definitely the easiest of the airports we flew through during that summer of disability.