I would taste the hickory smoke powder, yes, straight, and see how strong it is. Then taking a measured amount of rub, add small amounts and keep tasting until it tastes right. If you have it, use a 1/16 teaspoon measure and work up. You will get a sense of when it is right, assuming you have tasted your rub straight. In this manner, you will find the proper amount to use.
Although I like smoked salt, if you already have salt dialed in, you might want to use the hickory smoke powder instead.
"perhaps...but then again...maybe not..."
careful there son, those ribs are boiling hot...
(='.'=) Here there be bunnies...
Pacific Rim BBQ
Bob's Brew and Que