I do automation both pre-fader (on the clip) and with the fader. Usually pre-fader I'm automating for technical reasons - like reducing "s" sounds, funky clicks/pops, etc. With the fader I'm automating the performance.
Unless you mean before or after you apply vocal compression, in which the case would be after I've applied compression, otherwise how the hell are you going to know what to automate?!?!
I can automate with the fader, but I usually prefer the mouse. I automate with the physical fader when it's more artistic things like big swells on reverb returns and stuff like that. But the miniscule fader rides, I prefer the mouse as it's much more accurate.