I have tried a variety of methods and I can say, for my purposes, using chemicals was not the answer. Goof off/goo gone leave a slimy residue and even rubbing alcohol can make the task take longer. So here is what I do:
I remove all of the parts, same as you, including old bezel (I always install a new bezel for that freshly repaired look and feel), and find a good area to work on where the ipad wont slip. I then use a small razor set, the kind on a pen type handle, with the blade facing up (so it looks like a mini tint remover) and use downward force while keeping my finger on the top of the blade (away from the cutting edge, mind you) and scrape away the adhesive that way.
I do this for a few reasons. It being dry like this makes it easier to get all the adhesive off without it turning into little goo balls. Also, it helps create more surface area on the aluminum frame for the new adhesive to grab. It takes around 20 minutes to do the entire frame and get it near spotless.
I've done hundreds of iPads at this point and I find this method to be the best. I just do not like the idea of spraying abrasive chemicals inside of a device, that close to the board. And I got really tired of using tweezers and picking out those adhesive goo balls that are left over. That and the residue left by these cleaners never dries quickly enough, and will weaken your new adhesive.
Hope this helps!