I've noticed in a lot of online videos baristas will do a quick flush of the group before inserting the portafilter and pulling a shot. I'm guessing this is to stabilize the temp of the group. Typically I'll flush to clean the last shot followed by 30-90 second wait as I grind, dose, tamp my next shot. Should I also be doing a quick flush right before inserting the portafilter? Or was the cleaning flush following by the grind/dose time sufficient? I'm using a Profitec Pro 700.

I've been doing a 2 second flush before locking in the PF for 2 weeks now, but I can't recall where the tip originated for me.

Depends upon the machine and settings. Some DB machines (assume that's what you are asking about since you have a Pro 700 - HX's are totally different) are fine without any flush, but some may require a quick flush to help bring the group head up to temp. Experiment to find out what works best for your machine and then just be consistent.

Dan discusses this in his review of your machine. I believe it was flush, grind tamp pull. so probably around 25 seconds wait? The e61 DBs typically need a flush based on what your settings are due to the cooler water being circulated through the group while its idle compared to a hx

SonVolt wrote:Should I also be doing a quick flush right before inserting the portafilter? Or was the cleaning flush following by the grind/dose time sufficient?

The screen cleaning flush right before lock-in is common for commercial espresso machines; it clears the screen of old coffee and helps with last second stabilization. For semi-commercial espresso machines like the Profitec Pro 700, I recommend the screen cleaning flush 20-30 seconds before the extraction to give the brew boiler a little extra time to restabilize. As Brian noted, the Profitec Pro 700 Review includes more details.