If I get an EricS Therm, what technique might I use on a Pro 500 PID that should not require any cooling flush?
That depends a lot on what drinks you are making. For an EXAMPLE, if you are making straight espresso, you can set the boiler pressure to 1.00 bar max and you should be able to do a cursory screen flush (~ 1 second) and brew away.
If you are making 12 oz lattes, you might want a higher boiler pressure.
Lots of variables here and you need to be more specific as to how you plan to use the machine. Lots of info on my crude FTP site below my sig.