I fished the Moy many years ago for 3 years running with my company's fish club who subsidised the trips.
As mentioned, weather will play a big part and the Moy may not be fishable with fly in high water or very tough in low. Like it or not a spinning rod will be the best tool when the rains come, or go to a pub and drink Guiness till the cows come home if that's not your cup of tea.
A lot of the beats are more suitable to the worm (still very popular there as is the "flying condom" spinner and bubble and fly with spin rod ) so may be worth it to get a local guide to get you to the best fly water.
First year I went water was low and super hot so no fish, second, water was too high due to rains (though I did get a 15lb fish on a borrowed spin rod and a flying C) the third year was completely rained off and didn't even wet a line!
Some micro tubes may be good for the grilse and hot conditions.