Sometimes it helps if you remove all other alcohol from your inventory.
However, you do not really need to get him to drink. If you did, you could convince him you were friends, since you were drinking together, and he would tell you the password for the sentry at the second level of the dwarven mines. You can fight the sentry, though, which gives more experience than using the password, and it is an easy fight.
A little late, since you answered your own previous post, but welcome to the forum.
I appreciate the help.