SE High Speed Steel Drill Bit Set (15 PC.) - 82616MD https://www.amazon.com/dp/B000OVNS0Y/ref=cm_sw_r_cp_api_glt_fabc_WCGG6P6JVPVB8PC8XE3R?_encoding=UTF8&psc=1

Drill press would be ideal but the brass is soft, I used a tiny bit cooking oil spray, high speed on cordless hand drill as to not bite off too much and zipped right through. Used a flat piece of wood to keep removed orifice squared up, used a tiny dab of pipe dope when reinstalling orifices but only because I had it on hand.

Seven burners is a lot, might also be worth adding up the total BTUs and making sure your gas supply is sufficient. As in hose and pipe sizes and lengths feeding it. Or just make sure to use as large diameters and shortest lengths possible.