from my recent experiences, i would recomend buying 2 things. a jet spray carb cleaner and the berryman's carb dip cleaner. i would also recomend rebuilding the carbs at the time of cleaning, this would make things go ALOT smoother as most carb cleaning parts will eat and/or expand all of your rubber parts.
1st: DO NOT OPEN REBUILD KIT BAG YET! disassemble one carb including needle, float and choke. take/cut off old o-rings, gaskets and diaphram, throw them away. Dip carb body, float bowl, and all other odds and ends into the carb dip. now it depends on how gummed up your carbs are but i let mine sit overnight.
2nd: take parts out of dip. use the jet spray cleaner and spray out all of the little holes in the carbs, you should see the spray coming out of another hole somewhere in the carb. don't forget to spray out the choke holes, main jet and it's holder, float bowl overflow tube, and idle jet also. now what i did, i took all of the parts to my laundry basin and gave them a good washing with (don't laugh) laundry detergent and a toothbrush, i put a strainer in it too to make sure no parts went down the drain. now ur carbs probably look all shiny!!
3rd: while the parts are drying, disassemble the other carb, take off all o-rings, diaphram, and gaskets and let them soak. now depending on how long you think they should soak, you might have a little bit of down time between soaking and letting the other carbs dry but whenever the carbs are done soaking, take that one to the laundry basin and the dry carb back to the garage. now you can open the bag, separate the parts (there's 2 of everything) and start putting on the o-rings.
4th: i think this is where people get confused when it's really not that hard, it's easy to tell by the size of the o-ring to see where it goes. now i've heard of using grease to slip them on but i don't like the isea of anything other than gas in my carbs. to put mine on, i used a straight ice pic to kind of stretch the rubber into the groove, then rolling the pic around the part to seat the rest of the ring. put all of the o-rings on and reassemble the carb with all new gaskets. and repeat with the other clean and dry carb.
NOTE: I always got confused on how to put 2 parts back on the carbs, the choke and the throttly butterfly. the throttle butterfly goes into the top of the shatf when the counter sunk holes are facing the front of the carb. i've heard of grinding the butterfly but i don't believe that's its nessesary. now once it's inside the shaft, put the screws in, tighten them and back them out a little bit so that the butterfly is movable. this next part takes a lot of patience so bear with it, you have to move the butterfly around so that it's seated where if you hold the carb up to a light, you can't see ANY light come through. then tighten up the screws. now with the choke, i never knew which way to put the choke body back into the choke housing. the dot on the outside threaded piece goes towards the intake of the carb.
Hope this helps and good luck!