I have the Motive bleeder as well. I did the Volvo today and went with 15 psi. It seemed to work fine except for a slow leak at one of the bleeder hose connections which I didn't notice until I spotted a puddle of fluid .
It didn't seem to take much fluid, maybe 3/4 of a litre so I'm not sure if the ABS unit flushed out. The manual says the system holds about that much but when you consider the amount of over flow into the catch bottle it probably only took maybe half a litre in the system.
I used the ATE Blue racing fluid for no other reason than it's real easy to see when the new fluid is flowing out.
I'll be doing the Benz later as I saw some steel brake lines that look like they need to be replaced. I'll wait till it needs new pads and I'll overhaul the whole system.
Thanks for the opinions & info!

I believe it is very possible pop the reservoir off the master cylinder if you pump in too much pressure. Unless I'm wrong, while the lines and hardware might be able to handle lots of pressure, the reservoir set-up is generally not designed for much. System pressure builds on the hydraulic side of the MC valve not the reservoir side, which is normally subject to little if any pressure.