Here is an Amazon review for a popular anal desensitizing lube that will make everything clear:
Thanks to whoever invented this product! It works great! (Be careful though, I bled for like a whole day after using it). Make sure you take it slow then go a steady pace. Don't get too rough cause I was in a lot of pain for like the whole day after the 1st time we used it. But on the super plus side I didn't feel a thing during =)
I don't really have to explain here, do I? Okay...I might as well.
Pain is an indicator. It would have been an indicator for the "in a lot of pain" reviewer if he/she had not had a numbed-out ass during rough anal play.
Please do not use anal lubes with benzocaine or lidocaine in them just so you can go too fast with too large of a dildo with not enough lube. If it hurts you are doing it wrong. If you numb your ass, you won't know if you are doing it wrong. Ignore this advice and you might want to read about the world of anal fissures.