I would start by tackling the spray bottle first, the bottle is less cumbersome than a hose to start with.
Rub her all over with the bottle (or hose). If she gets upset here, don't go any further until you can rub her anywhere with the bottle. When the bottle is no big deal, she's relaxed and not caring, spray the air around her. It's helpful to fill a spare bottle with plain water for this step, you'll be spritzing a lot
. If she moves, move with her and keep spraying. Don't stop until she stops her feet and shows at least one sign of relaxation (licking lips, chewing, dropping head, blinking...), the stop spraying and praise her, rubbing her with the bottle. When you can spray the air around her and she stays relaxed, move on to her lower legs, following with the same technique as you did when spraying the air. As she gets more confident, move up her body, again using the approach/retreat technique. If you start with the spray bottle, you may find that the hose comes easier.
It's best to do this exercise in a roundpen or other controlled environment, especially if your horse is tempted to really bolt away. Hold the lead rope with the hand closest to the halter, and stand at a 45 degree angle to her shoulder, following in this position if she moves. Here you're safe from being run over, kicked, or struck at. Body language is pretty important here; you stand calmly, eyes basically down, "neutral," if that makes sense.
I hope this is somewhat helpful, and the best of luck to you!