Good sharp scissors, and take off a little at a time, as I am sure it is quite long now. Once you get it much shorter, it should probably be done by a groomer, but for now, you can scissor off the overgrowth, and that should help. It isn't like he's about to enter a beauty pageant, right?

If you live somewhere with a vet school nearby, you might ask if they know any places that teach grooming that might be able to give you a steep discount for letting student do the job!

How often do you bathe him? And do you use any shampoo, or just the baking soda?