As the CSA, I always fall back from WV, exfiltrating to the south over the mountains. I either send a fast mover to lead them to safety, or path the units individually; the general who starts there will get them fixed in place on multiple turns if you leave him in charge and they will starve, he is the worst (can't remember his name). If you play with historical attrition, those Volunteer brigades will need a depot to get to full strength, and I am not about to waste builidng one in WV just so it can get captured. Occasionally I send a supply wagon to meet them part way if they are having trouble getting away. Those guys can often make it back to DC in time for Taylor to show up and make the Volunteers into regulars.
Secondary tip, Taylor is around for three turns, so he can upgrade exatcly six elements. The most bang for the buck is for him to doit to those Volunteer brigades that you start with in DC and WV, plan ahead, and be very careful not to leave any conscripts in his stack. Alternatively, you could buy six virginia militia, combine them into two element units na d then have him train those, although it is more cost effective to upgrade the Volunteer brigades, since you have them anyway and they are pretty ineffective otherwise.