On Thursday, February 18, 2016 at 4:42:14 PM UTC-6, swalker wrote:
Moved last year to a place with no shop so I need to build one now
that most everything else is done. It will be concrete slab on grade.
I will use 2 X 4 sleepers on the concrete with plywood over the
sleepers.
My last shop was done this way and I liked being able to run airlines
and some wiring under the floor.

Assuming that you did this earlier, your actual question isn't about power access hidden in the floor. I have seen this in commercial applications and thought it was pretty slick.

Somewhere I saw a picture of a shop with a plywood floor and the
plywood had 2 or 3 coats of poly on it.
Anyone on the list use this approach.

Use the right kind of plywood, and coat it with a real floor coating. Regular poly isn't close to being abrasion resistant enough to make a good choice for coating.

You have a lot of choices in clear floor coatings, and even paint. When I was a kid there were several old shops I was in that had the wood floors painted with "deck paint" that was a super hard oil based enamel used on metal and wood at that time. It wore great and was easily repaired or renewable. With the newer products sold as "deck paint" or "deck coating" meant to coat and do minor crack filling on your backyard home deck, these products are more likely to be found as "marine deck paint" or "boat deck paint".

Robert