I'd love to know what the "proper" way is--unless you mean buying a DVD?
'Sir, please,' she said ... 'Will you not share your wisdom with us?'
'I have no wisdom,' he told her.
'Your experiences, then?'
'They have been trivial, uninteresting, and full of error.'
Ian M. Banks - Feersum Endjinn . It Ought to be Easy | Greasemonkey scripts
Depends. If they are a separate stream then you should just be able to turn off subtitles in the DVD/BluRay controls. If however they are baked into the file then they are physically white pixels and therefore could only be removed by editing each individual frame (there may be software to help this but you would need to make a decision for each white pixel as to what colour it needs to be to match the image "underneath" them.
I have had to do this for photos before where the date stamp was burned in and try and get it to match the surrounds - there are easier tools these days but for 20 photos it took me ages a while back (and as 20 photos would be less than 1 second of video that would not be fun).