I don't know any professionals, but I did our dryer recently. After moving the dryer and struggling for an hour to clean the vent from both the inside and the outside, I put everything back and there was no improvement. After some research, I found that the problem is often the dryer itself. I opened up the dryer and found a huge amount of lint in the dryer itself. After cleaning this out, the dryer works much better.

If you aren't up to opening and cleaning out your dryer, I've seen Dell's Appliance ((617) 625-1311) recommended on this journal before. I used them once for a microwave repair and they were very good.