Whenever my husband and I are in the mood for anal, we put dab some on the head of his penis. Most of the time we use it for our "grand finale", and by that point a good amount of my own juices have worked their way down to my anus, so the outside is fairly lubed up already. Again, this is just going off of personal experience, so it may not be the best choice for you.
(While I would agree 99% of the time with Gunsmoke that "there can never be too much lube", this story
makes me think otherwise. And a warning
: that link is NOT for those with weak stomachs, or for that matter anyone who doesn't like a good Tucker Max story.)