smoke flavoring spice

You can smoke sea salt with good results. Do not smoke regular paprika. It is a pepper that is smoked before being ground. You can also make your own liquid smoke.

Also go to your Mexican supermarket and get some peppers. Anchos poblanos jalapeno serano and whatever else they have and smoke them before grinding. Makes the best homemade chili powder.

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.

The amount I use is about 1/3 the amount of salt I use in my rub.

You can mix it with anything to give it a smoke flavor, but it's not as strong as Liquid Smoke. So, if you're using it in anything wet, use the Liquid Smoke instead, but for rubs and such as you're talking about I like it.

I make my own smoked pepper powder every year by the gallons. Follow these instructions but use milder peppers for smoked paprika:
http://www.bbq-brethren.com/forum/showpost.php?p=1263446&postcount=12