First off, Im thinking this has to be a typo, 800mg? This would be considered a very high dose! Standard HRT is around 100-200mg EW. Maybe 300mg tops. I could see a Dr losing his liscense for dosing this high. So I'm going to assume it is far less.
As for fluid control, you are on the right path, estrogen blocker! I prefer adex. The amount you need is based off of how much test you are on, how sensitive you are to estrogen, and how your body responds to the drug. Some guys take .5mg Adex 1-2x wk, while others use .5mg EOD. I would start with 2x wk and then get lab work done to see where his estrogen levels are in a few wks, then adjust from there. But really, by lowering the dose of test, his fluid retention will get better. Reducing test would be the first thing to do. And add the AI from there
As for how to cycle, 800mg is a huge cycle for a first timer lol! And not in a good way. He would want to increase the dose of test while on, in most HRT situations. If he really is using 800mg, thats not a great option. I think he should get this dosing under control first. After he gets his dosing under control, maybe consider adding in 400mg of Deca or EQ for 12 wks, with about 500mg of test. Then when the cycle is over, go straight back to HRT.