I, too, have 6 bays. I've always wondered about hose sizes for those 2 bays...if a smaller or larger size line/hose would make a difference in getting product to them quicker. Jeff_L do you tweak the size of your hoses to those 2 bays?
No - I use stainless steel instrument tubing for HP to all the bays. Above each bay is a manifold where all my LP product and air injects as Mep instructs.
I already had a programmable relay and a common air solenoid in place, so it was simple. I just had to add a ladder to the program to make the purge happen. It would be more complicated otherwise - you could use an existing air solenoid and isolate it with relays and control it with the same programmable relay, or possibly put together a whole separate system just like the anti-freeze purge.