Hi there!
When we want to change it up a little and not go with a traditional spice-type rub, this is what we do.
In a spice grinder/coffee grinder (by the way, DO NOT make the mistake and use your wife's coffee grinder, you will be in big trouble when she makes coffee the next morning!!!)...combine fennel seeds and black peppercorns. Or crush with rolling pin or in a mortal and pestle. Add minced garlic and olive oil to make a sort of paste. Rub this all over the pork loin and smoke as you have planned. This is an excellent flavor combination to pork loin. We love it!
An easy shortcut is to buy crushed fennel and coarse black pepper from our favorite online spice merchant. Living on a desert island such as Havasu, we can't find this stuff in a retail store. That eliminates any of the having to grind yourself.
Here is the link to the online store
http://www.americanspice.comSmoke pan we agree with all others in that it is personal opinion whether a flavored liquid truly makes a difference.
Hickory is quite strong for a pork loin. Our smoke of choice is alder. Imparts a nice mellow flavor that complements the above rub. We have also had excellent results from red oak and pecan with this rub.