Yes in your case I'd say hold it open until you smell gas. And even then, there still may be air trapped in the lines and the pilot won't stay lit.
In your case I'd say rig it so that the red safety valve is held open. Then come back to the machine and try relighting it every 10 minutes*. Eventually the line will purge itself of gas. Do leave a window open for extra safety.
*Close the red lever/valve (after it's been open for 10 minutes) and wait 5 minutes for the escaped gas to leave the dryer and the immediate area before applying flame/match (if you value your eyebrows and don't want a free and sudden brazilian wax).
Have no fear. The amount of gas put out by a pilot light burner is minimal and even when it escapes should not cause any problems. But it IS gas and one should always be cautious.
This will work EVENTUALLY, but be patient. I'm more ballsy and would purge the line on the dryer-end of the flexible connector, if the above daoens' prove satisfacory. But, please, do the purging at the pilot burner if you can.
THINK, be careful, and good luck!
DON'T PROP OPEN THE VALE/RED LEVER AND FORGET IT.
