Lemon pepper/brown sugar works good in the smoker as does a soy/sugar/ginger combo with some cayenne for heat. Marinate as long as possible. Smoke on low for a couple hours. Tuna can dry out fast so don't over do it, and remember albacore can be eaten raw so the red'r the better. Save the bellies to, they smoke up great.
For canning you can brine and then can or put raw tuna in jars. Add the olive oil then season as desired. Garlic, peppers, ginger, soy, bourbon...it all tastes good. You can add liquid smoke as well if you want that flavor without the hassle. The canning process will push a lot of flavor into the meat. Careful with canning and smoking the same batch, it can lead to overcooking the tuna. For canning I do 90 minutes at 10-12lbs and never have an issue with freshness.