two things u need to make sure your doing hun. firstly, the most most important thing is to make sure that you get the start coat right to the edges and make sure u cap the free edge because if you dont, when youv cured it, it will just shrink back into the centre. then when you put the colour on, even if you go right to the edges with that, it will still shrink back as it will only stay where the start coat was. hope that makes sence.
and also secondly, always make sure that you use the thinest layer possible of the colour. when i first started i used to do quite a thick layer (as if i was using a normal polish) and i couldnt understand why it wasnt curing properly and i kept getting bumps etc. now i only do it very very thin and if i need to do a third layer of colour then thats not a problem, at least my colour is all even and cures properly.
hope this helps.
Rachel x