I have three of those Craftsman tools. I tried one and decided to get a couple more for convenience and to have spare parts. Dirt cheap at Amazon.
They are a discontinued item and I think I know why. They all came to me broken in some way. Mostly it seems that the plastic used is brittle and prone to cracking. Sometimes it's on the outside- like the handle, sometimes on the inside - like the fan mount. I repaired them with crazy glue. They work.
The powder cups are a funky fit and are helped by a little light sanding in the right places, and will wear in to fit more smoothly. Don't force anything or it will break.
I've found that bumping the thing periodically with the palm of my hand keeps the powder flowing better, but sometimes you get a big burst right after and it's best to point the gun to the side for a moment.
I clean parts, bake them for 15 min at the curing temperature, clean them again, and pre-heat them to a temperature of about 250f to aid in the application of powder. If there is a spot that won't coat due to corona effect problems, then sometimes it works better to unclip the ground lead. The powder will stick to the hot part without a charge.
When I get the time I'm going to get a junk electric oven that's as big as I can find, but for now I've limped by with a toaster oven and done some larger parts by baking one end at a time, and by having the oven on it's end with the door open at the top and putting whatever I could find around the part to help help the heat directed at it. I always use the convection mode with the fan, so that helps.
Remember that the cure temperature the part temperature, not the oven temperature.
The tape that comes in the kit is not high temperature stuff and will get brittle and a little difficult to remove, but it works OK. I prefer the high temp. fiberglass tape.
Oh, I almost forgot - don't bake the parts indoors! Stinky!