Using firebox door as air inlet

Yes, you can. I do it quite often when the wind conditions aren't in my favor. Do a google search for Aaron Franklin's smokers. They don't even have intake vents on them. He just knows how far to prop the door open for good airflow.

Sure you can but you're loosing a lot of heat that way and your fuel consumption will be MUCH higher. You'd be better off putting in an intake damper, just make it big enough to get plenty of air into the pit.:wink:
P.S. If there is a sufficient bed of coals present a newly added split will combust pretty much immediately.:-D

I agree with Bill

the better you can control your air intake the better off you are.

do it right the first time