For distortion I use the dirty channel of my Tubeworks Amp cranked as loud I can without the feedback getting too out of control. On "Frank" I also used alot of delay for the section after the first solo. I also have a Metal Zone stomp box and a Dr. Jekyl that I used in a few spots and of course, the Wah Wah. That's about it. I prefer to use the distortion from a speaker rather than a stomp box. It's a little warmer and that is the great challenge when your trying to play an accordion like a guitar...warmth and volume. You are always right on the edge of going ballistic and creating a shrieking, unbelievably annoying sound that is guaranteed to clear a room in seconds. Sometimes that comes in handy, but I usually try to avoid that.
PS It also helps to duct tape the inside of the grill. This cuts back on the feedback. I also use a Boss volume gate that cuts off the mics when I'm not playing. This allows me to get about 30% louder on stage. So, crank it up and have at it.

Paul