Two years ago i sent my CV's in for vapour blast and then took them to have them U/S cleaned. Then spent the next three months getting them to work again. Soda blasting may be kinder because it is water soluble where the grit in vapour blasting is not.
The problem comes with the tapered capilliaries which turn 90 degree corners and have ball bearings punched in at those junctions.
Buy, borrow or make a U/S cleaner and put them in it four times different ways up. The cleaner only really works if the item being cleaned is in intimate contact with the vibrating base plate. If its deep dont stack them as all you'll do is wear slots in things that are touching other things. One body, its' bowl, top and the jets constituted a full bath (with Marks one anyway) You could buy one from ebay and then sell it back when youre done. I borrowed one from Taffus (thanks again Mark) and used it at home at my leisure and to my satisfaction. He also lent me his miracle potion the name of which i forget.
Make certain to remove the pilot jets beneath the alloy plugs in the float bowl, the float needle seats (with filters attached) and the needle jets. If any wont come out easily then U/S clean them which should loosen them and then try again. Punch the needle jets out with a soft alloy drift after removing the main jets.
Mine were done as i said by a U/S company and after cleaning them at home a further three times there was still blast media in the bath. Fourth time at home did the trick. The grey sludge is mainly sobubilised alloy parent metal so dont be too aggressive with them as they are getting lighter with each clean and passageways and working surfaces are geting bigger!!
Us an airline to blow backwards through the pilot air system from the inside of the carbs to the outside. Focus on the tiny drillings in the mouth on the cylinder head side of the carbs and confirm they are clear with a tin of wd40 using the straw attached.
I had quite a lot of brass swarf come out of mine in the bath. I know where some of it came from but cant explain it all. Some of it was as a result of drilling for the jet kit where they tell you to put grease on the drill!! Some of it also came from breaking the screwdriver slots in the ends of the pilot jets.
When fully dry; mix up a little araldite and put a tiny smear back on the surface of the exposed ball bearings where you will see just now some resin or sealer covering them over and creating a seal.
I painted mine with ACF 50 at the end. Its designed for alloy / aluminium and keeps them looking good.
AL
P.S. dont, whatever you do use washing up liquid to clean them internally as i did. It contains salt and after leaving them overnight to soak came back to a hideous frothy mess!!