Thinning cream cheese - what should I do?

I'm an up and coming hot dog cart guy and believe it or not, cream cheese on hot dogs around here is a staple and quite delicious! 
I want to use a frosting gun in order to dispense this stuff for speed and just because it looks cool - ha - but I'd like to thin down the cream cheese a bit to make it easier.  I'm already using whipped cream cheese and it's still a toughy to get out of the gun.  Of course I could let it sit out for a bit but the health dept wouldn't love that if they were doing a check.  If you've seen the Philadelphia Cooking Creme products that's what I'm going for (maybe not quite that runny) for consistency.  I'd rather make my own flavors instead of using something pre-made....
 
I thought about adding a bit of sour cream but not sure if that would alter the taste too much?  Perhaps there is a common other ingredient that is used to think cream cheese so that's why I'd throw up this post...thanks folks!