recipe calls for a grainny mustard, I have one more smooth, anyway to enahance? its to be used as a topping to salmon then put under broiler
I'd just use the smoother mustard. It'll be different, but it should still be good.
The smooth mustard will be fine. If you don't keep grainy mustard around buy some mustard seed and you can always crush it into the smooth mustard if you want to make this again.