Masterbuilt smokers are good entry level smokers, but as Jacksmoker was saying they aren’t built to last the long haul. I went through several cheap charcoal, electric, and gas smokers before buying my first Cookshack roughly 15 years ago. In the long run I would have been money ahead if I would have bit the bullet and bought my Smokette to start with, but we all have to go through what we’ve gone through to get to where we are today.
You really need to make sure you get all of the oven cleaner residue out of the smoker before you use it and as MaxQ suggested a vinegar and water solution is a good choice for cleaning it up. Before you use your smoker put some heavy duty foil on the lid of the smoke box, bottom and water pan. Then spray the grates with Pam. Those two things will go a long way in helping you with cleanup every time you use it. I also would purchase a disposable mortar tub from Menard’s, Home Depot, or whatever home improvement store you have in your area. If you soak your grates in water with some Dawn or other dish soap a couple hours after each use they will clean up quite nicely.
For more help and/or advice on a few quick, easy and cheap mods for your Masterbuilt you might want to check out this site