Advice Please

Hey all this is my very first post, didn't even know this place existed until a few days ago. So please be gentle :). Ok here is my situation. I have a Brinkmann Smoke n Grill (Think some call it the ECB) i bought it last year and have used it many times using ot for ribs chicken pork loins made  brisket once. When i bought it i did all the mods that i had watched on You tube. it has worked well when i have used it.

 However from the get go i have had trouble with the heat either too high or too low. while the food has come out great, I did find that I went through charcoal rather quickly. So as i was researching again on You tube, i came across a brinkman conversion kit. It would make your charcoal smoker into an electric smoker. I have been reading a few posts here that recommended using sand(which is what I was using in my smoker currently.

 I am planning on converting it over so my question is, I saw somewhere where someone added lava rocks to the smoker either just under the electric element or over top. Would the lava rocks work the same if I were to add them in the water pan? Or should I stick with either the water or sand? Also any other recommendations you could give me for switching over, like what I should be aware of. Do I need to cover the holes in the bottom of the charcoal pan?

Anyways thanks for allowing me on the forum and cant wait to read and pick up some reviews for new smokers and recipes