Training In The Shower

I was having a shower myself tonight, and came up with a great idea.  I want your oppinions on it.
Sometimes when Ushi comes in from a working day, she is quite muddy.  (she tends to pick up dirt easily).  My sister would want to have her paws washed if she is really dirty.  Ushi hates this.  She totally stiffens up even before she is in the shower and before the water is even turned on!  I sort of have to really drag her into the bathroom lol.  Once she is in the shower, my sister washes her to make sure all the dirt is off, but i would be there reassuring Ushi.  I also dry her off.
I’ve come up with a suggestion though to see if I can make it more of a positive experience.  I would like your feedback on this though.  If it’s crap, tell me.
I was thinking that maybe I could maybe start once a day maybe just getting her to go into the bathroom, for example.  I was thinking that I could even start by either having her on the lead, and treating her if she walked in nice and relaxed, and gradually getting her further and further in (it’s not a big bathroom).  I was then thinking of then trying to get her into the shower cubicle (we don’t have a bath).  I would then gradually turn the shower on, and then if she was still relaxed, then treat.  I would increase the sessions each day as well as working, and gradually take her off the lead.  If she showed any sign of not liking it or getting bored or whatever, I would stop instantly.
What do you think?  Would it just be cruel to do this?  I’m thinking though so that if she does need a shower it’ll be easier and more pleasant for her.  (I haven’t used shampoo on her yet).
Please give me your thoughts.  If it is pointless, I won’t do it.
Thanks for your suggestions.