The trick I have found that works very well when using polyurethane glue is to go back and remove the excess from expansion with in 30 to 45 minutes. At this point in the curing process it is still soft enough to pick out but not sticky enough to cause a mess. (you can touch it with your finger and it's not sticky) I usually use and Xacto or razor blade to lightly score the lines I want to keep and then pick it out.

If you have the room around the work piece, knowing that this type of adhesive is going to expand, try using packing tape to control it. In other words, apply the glue to one surface, moisten the other with water, and mount them together as required. Take small strips of packing tape (pre-cut for the space available and ready to use) and with a putty knife or other thin straight edge, apply the tape over the joint. There will be a little expansion under the tape but most will be at the ends. Do not cover or try to stop the expansion out of the ends, as it has to expand somewhere. This controls and limits the expansion and you only have to pick the excess from the ends of the tape in about 45 minutes to an hour (dependent on humidity in the air). Let the glued joint cure overnight and gently remove the tape. You will find a nice clean, slightly bevel filled joint that is extremely strong and light.

If it has already cured, you're going to work at it. In my first few projects, I made test pieces trying to learn how much is enough and how much is too much as well as a satisfactory cure time for easy removal. I let one test piece cure overnight and even went as far as to use the Dremel with a small sanding drum to grind out some of the excess. Not and good method but if this is where you are now, you may have no choice. Just use a slow speed, light touch and grind away small amounts at a time so as not to hit the structure you were gluing together.