My buddy and I put these in all the time. He digs them with a skid loader. Keep them in the woods (shaded) to minimize evaporation. The Benseal is an excellent idea (heard about it, but didn't know the name..Thanks Steveo)we have always lined them with heavy-mil plastic, then back-filled about 10-12" of dirt over the plastic, driving back over the dirt as you go to pack it down. If you don't backfill, the deer will punch holes in your liner!
It depends on your site, but they can fill up in a hurry. We've dug many about this time of year and had excellent hunting near them within weeks. You need one or two good rains is all. Its surprising how little water will attract deer. The key IMO is keeping them in or near security cover. And they get better and better close to the rut. We have even had deer come in the winter and paw at the ice, trying to get a drink...
Good luck!