I agree a lot with what Uwe has said. Unless you have the chops of the mighty and wish to develop your own distinctive fretless style (Good luck with that btw) you need to tread the line between "Playing too accurately without any meaws" and (over playing ) sliding every note because you can.
Someone on this forum when I first joined made the point that when you begin playing a fretless the best thing to do is to "just play the damn thing like a normal bass". This IMHO is the perfect approach.
I have been playing a fretless bass for about 25 years and the way I try and keep my fretless chops is to make sure there is always 1 or 2 songs in the bands set that I can tastefully use it on.
The Crocs version of "Cant always get what you want" that I posted recently was played on my Cargill Fretless, even though the photo's that I used to make the clip showed the Jazz and Explorer.
I'm sure a lot of you have better ears than me and can hear me playing a few not quite perfect notes but as Uwe says the odd slightly sharp or flat note aint the end of music as we know it.
Its more about training your ears than your fingers IMO. If it sounds slightly flat then slide up to the correct note and after a while you start placing your fingers more accurately AND you train your ears to be more sensitive to pitch. You can get it so that the slide up actually sounds intended with a bit of work.