I saw a lot of mixed opinions on Hydretain, so I didn't want to spend the money. Also it's crazy to think that a wetting agent can maintain activity in soils for 3 months (label says 9 oz/M every 3 months) so it may not be a bad product but it just needs more frequent application.
I am currently doing a 6 month trial of Soaker Plus from Helena. I'm applying it to two lawns and I also have plots set up including a control. 8 oz/M bi-weekly April-October on TTTF. I'll write up a post following the trial soon, but I think you should look into Soaker Plus. It's made by a serious company in the turf industry and I know there are supers that use it. Not all wetting agents are the same, some move water and some hold water. Soaker Plus is a holder and isn't phytotoxic (it doesn't need to be watered in immediately) and if you want help managing water and drought stress you need a chemistry similar to this one.