For what it's worth you don't need to know historical vol to trade vol, although it might help. As a mm you can for example sell high vol and buy vol in different strikes and ofset your delta's, you can trade vol in different calender months to ofset your risks.
As a trader (I don't trade options much anymore) I used to sit on the bid and the ask of options on DIA (the tracker of dow jones) and hedge my delta's and go along with the flow. If I saw people were buying options I adjusted my vol in my model and adjusted my prices accordingly, if people started selling options I did the reverse. I was making prices in 20-30 strikes. I didn't have much of a view on vega, I just went with the flow.