Turning away in training

I was always told that when a dog jumps up at you , the correct way to deal with the situation is to turn away and ignore it. Now that's fine in principle , however when you have a boxer that spends more time on two legs than four , it becomes a problem! Our local park of currently like a mud bath - and im guessing that most other parks are the same at this time of year. Unfortunately, when Polly gets excited , she starts jumping up at me , covering me (literally) head to toe in mud! Every time I go out with her now I have to come straight home and put all my clothes in the washing machine , nightmare! Ok , so ways of dealing with it.. Well , I could tell her off , but to be honest she thinks that's a game and jumps even more. I could turn away and ignore her, but again shes persistent .. keeps on jumping and continues to make me look like the mud monster of the west. Or maybe a training spray? , I have tried one of those small red 'Pet corrector' compressed air cans - she thought that was highly amusing and started jumping around the park like a kangaroo. The quest for a training solution continues , I'm going to post a video of her doing it soon .. stay tuned for a laugh.