For many years, I've replaced brake/clutch fluid using a large syringe full of fresh fluid and filling the system from the caliper/slave nipple, having first emptied the mastercylinder with another syringe (so as not to contaminate the fresh fluid in the clean syringe). As fluid travels up the hoses, air does not get trapped anywhere and if any had been in the system before, it appears as a bubble in the mastercylinder on its way to freedom. The main precaution is simply to keep an eye on the fluid level in the m/c so it does not overflow. I've not found any drawbacks, the reverse, I find it quicker and successful first time, every time. Do many other people use this method?
Depending on the system I sometimes conventionally bleed or reverse or a combo of the 2. I usually empty as much of the system as I can to get rid of the old fluid, before I put in new fluid, just not a fan of pushing in new fluid and hoping. It is a right old faff though bleeding it all again, especially the Duc's rear brake John
