This is an old discussion, but since it stopped with an open question.....
Fingering is a significant part of technique of a "piano" keyboard instrument. There's a reason why pianists practice scales and arpeggios. They help to get thumb crossings smooth, fluent and in time and to provide a toolbox so that you don't run out of fingers as a tune heads in one direction! I guess "bad habits" are things that seem like short cuts now, but will hold you back later. They'd include things like missing fingers out unnecessarily, ie going from finger 1 to 3 when the interval is a third, and hopping (and hoping) when jumping from note to note where there should be a thumb crossing.
Whilst it's important to be able to thumb-cross fluently there are some tunes that can be played with none if fingering is sorted out, which can be a useful exercise. Blarney Pilgrim is one.
It's not a style I'll ever play, but I find this video quite inspiring
https://www.youtube.com/watch?v=OEOCe4bcOR0I'm certainly no expert but as time goes by I do feel that fingering just seems to become more and more instinctive.
Good luck!
Tom