it was all done using manual focus, i honestly don't think i've ever autofocused with any lens on my t2i-- i'm about 90/10 video/pic and when I do snap a pic I just manually focus like i'm used to.
When i'm shooting action like that I tend to use the aperature most to control the exposure and leave the shutter and ISO the same throughout (unless for some reason I need to bump the ISO a bit). That said, the follow camera angles I try and keep the aperature around 6-9, but some of the tripod shots I got away with a 70-200 f4l with the aperature wide open.
Hope this helped! Also, I have a much much better ski video on the way that I shot today and yesterday. Can't wait till I finish throwing it together
Canon 7D MK II -- Sigma 18-35 1.8 --Canon 17-55 2.8--Canon 50mm 1.2L-- Canon 70-200 2.8 IS II