evworld, how much jerky are you putting into your Masterbuilt Smoker. You should allow at least 1 inch of space between each strip to allow the smoke to circulate through all the jerky. You should do fine smoking it at 180*- what you're doing is drying out the meat while introducing smoke to the meat. Weither you apply smoke the whole time or not depends one your preference. Some like just a bit of smoke that doesn't hide the flavor of the marinade and others like very smokey.
After 90 minutes or so, check the meat-the finished product should be dry but flexable. Test it by twisting or bending a strip, It should twist or bend without breaking-a few tears along the grain of the meat is okay- and then return to it's orginal shape. If you twist or bend it and you get a lot of tearing and the meat stays twisted or bent then it's over dried. Keep in mind that the thinner strips will dry faster than the thicker strips-remove the strips that have dried to your liking and continue drying the rest. I usually recheck the remaining jerky every 30-45 minutes and pull the ones that are dry. Depending on how much meat you have in your smoker and the size of your smoker the process should run between a couple of hours to 4-5 hours.
Also before smoking, I allow my jerky to hang in the rack at room temp for about a half hour to allow the marinade that is on the surface of the meat to dry a bit. There is a technical name for this drying proccess but it escapes me at the moment. The theory here is that the smoke flavoring will adhare to the slightly dry surface better than a wet one. You may want to experment this for yourself and see what you like better.