Depending on the age and engine fitted to your Izy, the brass central bolt that holds the float chamber on is the main jet - it has one hole drilled down its length, and another drilled across it to connect. Fuel from the float chamber passes through this jet on the way up to the emulsion tube.
Peering up the emulsion tube hole, if you can see a screwdriver slot then undo it, and the tube slides out.
Although compressed air is obviously the best, an aerosol carb cleaner will have to do - it should work.
Take note that the float chamber actually has a step on it (usually) that the float drops into, so its worth marking its position! Don't lose the rubber 'O' ring that seals the bowl to the carb body.
The other screw in the float bowl is there to allow you to drain the float chamber if you need to - the slightest ingress of water at any time causes rusting in the float bowl.
Redex (upper cylinder lubricant) isn't needed in any way.....unless you're talking about a carb cleaner made by Redex!
At the risk of sounding like a true anorak, you have one of the best machines around.
John