ok this is my thought on the matter, hes known you for all these years and prob seen you at your worse and day to day...
so you have to make a real effort, show him how hot you are, so him a different side of you, then that will keep him hooked and it should all go well.

also try and get him to dress up really nice then you can both be saying how hot the other looks, and that can then lead to the flirting

As an afterthought (since you've probably already decided what you're going to wear, where you're going, and when the wedding is), does he see you as 'one of the lads' when you're out doing things as friends? What sort of things do you do when you see each other? Are you in a big group of friends, or have you spent a lot of time with him on your own?

Yeh, I can see you scrub up nicely

Listen, I don't want to be a party pooper, but in my experience when someone sees someone of the opposite love as 'one of the lads' it is more difficult to switch from being friends to something a bit more intimate.

I think a bit of subtle matchmaking from your friends is the best course of action here.

Flirtbox Agony Uncle