Just about all of the parties we go to (including our own) have extra SMs to make this happen. Not all guys want to share a girl in this way though, so there are no guarentees.
I have a close male friend from a couple we know that enjoys doing women with me where we both take turns in her mouth and pussy. If one of us is doing a girl and the oother is nearby, we'll ask the girl if she wants another guy to join us, and more often than not, the answer is a definite "Yes". We also realized that most of the women we know (including our wives) like multiple men. Most of the guys we invite to our parties are good with being 1 of X guys pleasuring a woman.
I have seen and been to parties where this is the focus of the party. Not really a gangbang but more like a guy heavy (i.e. 2:1) party. I had one planned but had to cancel due to a death in the family, then Covid ramped back up, but do plan to have parties with exactly this purpose in mind.

