If it evaporates, look for a green stain on the manifold...

Well I snugged up the bolts, but not before trying to investigate by removing the hose clamp. Needless to say I spent a little time cleaning the antifreeze up in the engine bay and on the garage floor........

Silly boy....

Lern frum yer mistakes, son...lern frum yer mistakes....
You never actually said, but did you suspect, or have a leak there, Dan?

There was a little coolant present on the manifold.....lots when I loosened the hose clamp and pulled the hose away.  ( I never claimed to be the sharpest tool in the shed) ......

Again bringing up this subject....

I had the same problem, I take a sheet of wet dry sand paper lay it on a piece of glass flat and take the housing and place it on top of the sand paper, keep it wet and sand back and forth. You should see the high and lows from the sanding in just a couple of minutes. Just keep moving the housing back and forth keeping it level untill nice and smooth. I do this everytime I put a motor together even with new housings you will be surprised to see the uneven surface on these housings.

I'd try the sand paper method..it does work..you may have a cracked housing though since you keep snugging up the bolts..I just did my thermostat last week when I did the manifold and it doesn't leak..use a block sander on the manifold too just to touch it up..and no silicone!!! Just touch the bolts snug as it doesn't need to be that tight..put some lube on the bolts too so they don't seize in the manifold too..also make sure your thermostat is seated in the recess in the manifold...how much to drain..I jack up the pass side and drain about a gallon out then when I remove the hose I lift it straight up to drain what may be left in the bottom part of the hose which isn't much...if you do it right none will spill on the manifold.