I'm sure there are a few different reasons that the shellac hasn't lasted on you - not sure if washing your hands would make too much difference as I wore shellac on hols for the past two years and thought that the in and out of the pool would affect it, but it actually lasted the whole 15 days (and a couple more when I got home!)
I have had a couple of issues in the past with it peeling off, but I think that was because the therapist wasn't careful enough putting it on. If the gel comes in to contact with the skin on wither side of your nail it stops the gel from adhering properly to the edge of the nail and so it starts to life after only a day or so.
Trial and error really - find a good salon I suppose! Also I did the gelerations once (not by choice - I booked shellac and they didn't tell me until I got there for the appointment that it was actually geleration
) Did a good bit of damage to my nails as they file it off rather than soaking it off - she was a little vicious and my fingers were sore for days!!!
Hope you find one that suits!