I've got to step in here... you never want to push the dirty, contaminated brake fluid back into the master cylinder... always open the bleeder and than compress the caliper... once you've the brakes back together start with the longest line, (right rear) and either draw the old contaminated brake fluid out of the caliper and line with a vacuum pump or have someone help you bleed the brakes... you need clear brake fluid...
Any dirt or contamination that goes back through the master cylinder can damage the sealing surfaces of the piston in the master cylinder and than it can't function correctly... .
I just did the rear brakes on my 05 and bleed the brakes. . it took almost 2 quarts of fluid the get the system to run clear at all 4 corners...
Its my personal opinion is that nothing is more important than working brakes at 60 mph when the guy pulls in front of you and you've to slam them on... .
Just my thoughts. .