hey fella !
done a few of these myself always try to keep the due date for these a bit open ended so i can slide them in on a rainy day (get somone on the bottom of your ladder),
i always find bucket of warm water , fairy liquid and a tesco microfiber cloth (£2 a pack, 2 in a pack blue ,green ,yellow or pink if your daring!!!) will shift most muck. but i always carry a bottle of fairy power spray (tescos £3 50ish) and small dustpan type brush for brackets and elbows all this kit will last for ages and leave my job looking sparkly.
Good luck
Cheers Tom