Generally speaking, the more water you add to your chocolate, the lower it's shelf life will be. It's hard to discern your exact goal, but if i'm inferring correctly, you've got a solid chocolate (bar, someother form - you're not talking about a ganache center i don't think). If that's the case, iand by smoother you mean you are not happy with the melt quality - i'd be sure you start with a fine particle size chocolate (< 20 um) and you can begin to modify it by adding anhydryous milk fat (or ghee). milk fat will make it softer, harder to temper, and melt more rapidly (often referred to as 'smooth').
Do not add much - perhaps 1%, learn how to work with it, taste it and see if you're happy with it. if not, add 1% more, repeat..