Yep, it is a tricky balance between airflow and fuel/gas produced. Not only is the volume of air important, where it is applied, and how it mixes with the fuel is also important. And of course more is not better as this can cool down the burner and effect how the gas is produced. One thing I figured out pretty quickly is you better have the finished flue in place to experiment with. Any changes to the flue mean that all that trial and error you did getting it to burn right probably just went out the window. That is one of the best parts the gentelman in the above linked videos points out. I think it is also good to plan on covering/enclosing the burner section in a box with a single air inlet that can be ducted to the outside. Depending on how well the building into which this is being installed is sealed, whether doors and windows are open and how far can really effect the draft in the flue. If you duct in the combustion air, the state of windows and doors will have no effect on the burn. It will also help keep the draft from one of these monsters from pulling cold air in thru evey leak in the envelope of the space you are trying to heat. IT is also safer, if you work on vehicles and accidently spill fuel, the vapors on the floor are going to be drawn to this heater and could possibly be ignited by the burn pan, blowing off the aformentioned doors and windows in a gross and viscious fashion:)
I have been playing with this type burner lately and it has been tricky to get it to burn consistently without adding forced air. The main advantage of the forced air is the turbulence it can be made to create. That is where the holes seem to work the best over other air inlet methods, They create more turbulence. Some swirl in the burn also helps, but too much dosn't:) What I found is the more noise it makes, the better it is usually running, but making changes is real hit and miss as it can be a lot of drilling just to find out it dosn't work any better, or works even worse...
One thing I found is that a curved bottom burn pan is usefull. Since the gas produced is a factor of the temperature and the size of the oil puddle in the pan. In a curved bottom pan, the size of the puddle can be varied by flow rate to help taylor the gas produced to the available airflow for a clean burn.
Fuel flow can also be a problem. Most of these I have seen have a jug feeding the burner from a shelf or bench. Gravity while readilly available is not very consistent when powering a fluid that changes viscosity and flows better as it gets warm... I ran into this when building my babbington. As it warmed up, it would run away and required constant throttle adjustments. I didn't want to use a fuel pump so I settled on a lightly pressurized fuel tank on the ground. It seems to give me much more consistent oil flow as the garage warms up.
