The drain plugs are on the side of the carburetor's float bowl. It is a small brass screw. Place some paper towels under the screw to catch any fuel.
The carbs are pretty straight forward if you need to take them apart and clean them. There aren't any complicated "gizmos" inside them. Just a float, jet and the emulsion tube.
Make sure you clean every single passage. Remove the idle mixture screw on the side as well as the steel plate on the top so you can clean the passages.
Count the number of turns required to lightly seat the idle mixture screws all the way in. This will give you a reference point for the adjustment.
I've cleaned literally hundreds of these type carbs over the years. IM me the serial number and I can IM you the carb rebuild procedure as well as the synchronization procedure.
You will need to re-synchronize them after removal.
ETA - Part #24 in
this diagram is the drain screw. The main jet is part #26. Part #12 is the steel plate you need to remove to clean all the little passageways.
You don't have to remove the throttle plate and shaft to clean, just the float bowl, float with needle, main jet, idle mixture screw and the steel top plate.
Make sure the float height is correct when re-assembling.
If you are careful, you can re-use the gaskets if necessary although it's best to use new ones.
You'll need a timing light to verify/adjust timing.