Miller maxtar 150 stl

I do stainless food service sanitary tubing for a brewerey.
We use a miller maxstar 150 stl lift arc with a foot pedal.

the biggest problem we have is purging.

We dont have a purge monitor and usually just use a bic lighter.

Is there a better way to check purge than a bic lighter?

BTW , the miller maxstar is working great but occasionally, we need to burn 6010 for supports. IT doesnt do so good.

our lincoln inverter works better for 6010.

Also , have noticed that when a stainless steel weld turns grey, it rusts later on...does a gas lens help?