I didn't tape anything, personally. If you do it right, I don't see why you need to tape the speaker (there is a good chance it will run down a side and onto the back, but this wipes off).
Make sure whatever surface you do it on is 100% level. If you don't have a level the cheap way to do it is to put the glue bottle on it's side, rotate it a few times (45 degrees per turn), each time checking to see if it rolls. If it does in any direction, it's not level - Find another surface.
Look closely at the jig. There are arrows on either side of the long sides - These are the alignment arrows for tilting the glue. You want the *center* of the glue to go just past these arrows before you remove the pin. Don't remove it when the edge of the glue reaches it. Finally, WAIT. 3-4 minutes is not overkill - let the glue fully disperse, you'll see it suck itself all along the edges.