I don't like Liveview very much, focusing is too slow for me. I use my 50D/Subal mostly for macro, and I shoot only in manual. Hence no need for metering since you won't be able to meter the flash very well. The way I shoot is to set the shutter speed at 1/160 or so or 1/200 if I want a black background and the aperture to f11 or f16. I use an optical trigger to fire my flash so I get TTL from the internal flash. No picture that I shoot macro is ever more than 1/3 stop over or under. Before I had the housing converted to optical, I used a TTL converter from Matthias and it worked just as well. Before that, I simply set my strobe somewhere in the middle of its power and shot, looked at the histogram then made adjustments to the pic. Once you shoot it a while, you will get a good feel for exposure; most guys shoot in full manual mode with good results.
Bill