After messing around some, I pretty much came to the reality that the floor was a hold up. We got a nice break in the weather this weekend and it's supposed to be near 80 next Saturday, so I decided to attack the floor problem. Ow, my aching back. To start with, I had to empty the place. So Saturday I got started on the job. Cleaning out the barn took about 2 hours. Once that was done, I swept it up and started hosing it out to clean out the dirt, etc that accumulated while the building was open. There was a LOT of crud in there. After the third complete wash out and sweep, I did the first etch. Ya - first. I used some "low voc" acid I found at HD. I thought a gallon should be enough as the directions indicated 24 fl oz per gallon for etch. Second mistake - thinking the nylon push boom would be enough to move the etch solution around. The solution did fiz, but only for a short time. And the broom wasn't very much help. But I managed to do the whole slab. 10 gallons of mix and I just barely got to the end. I rinsed it twice more after that.
When I got the etch at HD, I bought a nice 24" squeegie. Do not do this without one, it's $18 very well spent! Brooms are BS, the rubber squeegie move water around and out quick and clean.
Today we had off, so I go inspect the floor. It's clearly not dry enough to paint. I'm just not satisfied with what I see, so I go down to the local hardware store and pick up two gallons of muratic acid 31%. I also picked up a new 9" roller frame and a 1" thick roller. What the last etch did do was show up a bunch of "puffs" - bits of concrete that looked like they would pop off if rubbed just so. I put a fresh 60 grit flap wheel in my 4" angle grinder and hit all those spots. Then I found several places were sap had dripped off the joists, so I cleaned those up too.
I mixed this new etch at one pint of acid per gallon of water. The math says thats one part acid in 8 parts water. I pre-wet the floor this time, worked in sections and slopped/moved the etch around with the big furry roller. Mucho better all around. This etch solution attacked the floor better and lasted longer. I "mopped" each section for about 5 minutes, then rinsed it well and moved it out with the squeegie. I worked door side to the back since part of the slab slopes in the general direction of the door. After 3 more hours and a couple more rinses I called time.
Even after all that, there are still a couple of shiners that the angle grinder can touch up. Now if it'll just dry up by next Sunday, I'll be in business.