Walls and Ceilings - Routing around electrical boxes

When I drywalled our kitchen, I cut out holes for boxes PRIOR TO hanging the board. Invariably, I was off by half an inch or so. Then I learned that you can cut the holes with the board pressed against the wall, using a roto tool like a Dremel. Two questions: how do you do this and can you use an ordinary hand router (I don't want to buy a Dremel just for this).

I would not use a normal router for cutting drywall. If you want to save money, just get a drywall saw and cut with it. It won't be as fast or neat as a dremel tool, but it will be inexpensive.

The key to routing elec boxes with a router is in the bit, not the brand of router.

It's best to use a Guidepoint bit in your hand held router. Tack your sheet up to where it's firmly pressed to the box, but not too tight or else the cutout will blow out at the last edge you're cutting.

Prior to hanging the sheet measure distance to the center of the box from a known point & mark accordingly with pencil. After your sheet is up in place, mark the center of the box & plungein at that point, for a begginner, I'd recommend routing around the inside of the box completely then smack the sheet with your hand & the cut-out will pop out. Then you can see the box & simply run your bit once more around the outside edge & you've got a perfect box.
Another tip, when your bit is on an inside edge, always run your router clockwise, when you're on an outside edge reverse your direction. Also works great for doors, windows, cold air returns & heat vents.

A word of caution, hold the router very firmly, & be advised you'll probablly screw up your first 5 or 6 attempts, so nail up a scrap over a box & practice a bit. Also only try to route vents that are metal, the router will eat fiberglass ducting for lunch quick!

Once you get good at it you can use this method for trimming sheets for out of square walls etc in a jiffy. It does speed things up considerablly. ;)