I just do it last after my system is full of RV antifreeze. Then I go out, take the screen off of the city water inlet, and poke the little plunger in the center (with the pump off). The RV antifreeze shoot out of the line. Then put the screen back in and close it up.
2021 F350 Lariat 7.3 4X4 w 4.30s, 2018 Wildcat 29RLX
2012 BMW G650GS, Demco Premiere Slider
1969 John Deere 1020, 1940 Ford 9N, 1948 Ford 8N
Jonsered 535, Can of WD-40, Duct Tape
Red Green coffee mugs