Have HVAC Questions? Ask an HVAC Expert for Answers
An easier and safer way is to just hold down the pilot button until you can smell the propane. In this case, the pilot button acts as a bleeder valve and you don't have to worry about unions and cutoffs. In addition, this takes zero tools and you won't have to worry if you have re-tightened the union properly when you're done.
How to bleed air from gas lines in a propane furnace?