If you have plenty of fluid, (always have and extra liter or quart of fresh fluid), you can just open the brake bleed valve on the opposite side you are working and let it slowly bleed some old fluid out into a pan. Gravity is at work here since the reservoir is higher, it will slowly push fluid from the reservoir to the calipers as a fast drip. If you have a way to suck out most of the old fluid from the reservoir and keep filling it with new fluid, then it will go much faster since there is less old fluid to slowly bleed out overall. Also, if you break loose the bleeder screw before removing the caliper and then open the bleeder and push the piston back in while aiming the bleeder for the drain pan, there will also be less old fluid to bleed out later, rather than pushing the old fluid back up into the reservoir. If you can remember to keep the reservoir full while gravity bleeding the opposite side you are working on, when it's time to ask the other person to SLOWLY pump the brake pedal once or twice and hold to bleed, you will be already into new fluid by then and very little pump bleeding required.