Frosty, i think it doesn't only hydrate and keep your dog hydrated enough for the next training, allot of water is also the best thing against water retention. I was training the same dog im going to train right now, 1 year ago, together with the one i was keeping on raw. Because that one got injured. This one was on kibbles and i kept checking his skin every day, it would bounce back in 1 sec. First i added like 700 ml to his feed, then 600 then 500 then 400 and his skin still bounced back. First he would work great and recover fast but as the days went by he could take less work and still not close his mouth after 30 min cool down, in the middle of the winter. He was rested just fine. I'm 100% sure his muscles started to retent water because there was a lack of. Meanwhile the injured dog got sick also, he dropped to 18,9 kg (20,5kg) Once he got better i still didn't train him but i started to give 1000 gr of raw and added 1 liter water on top of that, every day. The day, i had to chose between the 2 of them. Dog that was injured and sick crawled back to 20,3 and felt even better then before he got injured, while he wasn't trained for 4,5 week. Maybe it wasn't the wisest thing i ever did to take any of them 2, but he still caught his first boar in 2:14 It also works the other way around, when the muscles are already holding water, give allot of water will help to lose that.

The method your friend is using sounds perfect to me. Thanks, think i will do something like that and remove the bowl 3-4 hour's before the training.