without a mech, yes, you can just torch the top part. I have a mech and I go ahead and torch it anyway. How long does the mesh last? I don't know, I'm still using my same wicks after at least 2 months. After every couple or so tanks and when I want to change a flavor, I use a syringe and flush the tank several times. Then I do a dry burn, holding it upside down so the water and leftover juice wicks down the wick and is burned off. This burn also helps clean the coils as well as the wick. I'm always recoiling just for practice so my coils don't last very long LOL.. but I've heard of others who very rarely recoil.
to oxidize, I use a regular "wind resistant" lighter from walmart.