First , I would never just rebuild one front caliper. They are so simple to do that when you take the first one apart to re-do, you will be ordering another kit to do the left side. Especially on front brakes, you can have brake pulling problems due to one rebuilt, free moving caliper and one,sticky,not so free moving caliper. I would also replace the front brake hoses as well...you are already taking them partially off to rebuild the front calipers and you are doing a fluid change.
To get the most old fluid out first from the master cyl, I bleed down the brakes untill the resivior is just about empty. I then refill it and go for it. My $.02 Chris

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.