You could do a screed system like you suggested but you should attach them with a power actuated nailer (Ramset) but the best way is to use plywood that you ramset to the concrete. For a high moisture area ideally you should put down a 1/8" layer of cold cutback roofing mastic on the concrete, then #15 roofing felt over that. Then ramset down the plywood and add another layer of #15 roofing paper over the plywood. Then nail down the hardwood. You can substitute poly film for the roofing paper.
In really wet areas they will use cold cutback mastic + #15 roofing paper + another layer of mastic over the roofing paper = making a sandwich. Then ramset the plywood and a layer of #15 roofing paper then the hardwood.
The idea is to use the 2" hardwood nails at the proper angle so as not to run the nail all the way into the concrete. Moisture can wick its way up into the wood if this is done.
It is a tedious method but very worth it if you floor is expensive and/or you don't want to do it again.
My home is on slab and have hardwood in most of the home done in this fashion.