Another Way
If you can’t have a mock viva or don’t want one, there will be another way for you to rehearse talking about your research. Give a seminar, go for coffee with a friend or just chat with people about what you’ve done. These actions are not the same as a mock, but they help in the way that a mock does.
If you don’t want to read your thesis in preparation for your viva in the way that your colleague did, then think about how you could do it. They did a chapter a day? Maybe break it down into sections instead. Or maybe take an afternoon off to read it all. There will be a way for you to do the work.
A lot of really helpful viva prep advice gets swallowed in the specifics of how someone else did it. Find your way to do things like read your thesis, make notes and summaries, rehearse and so on. If your friend’s way won’t work or you can’t follow the advice of the person on the internet then find another way to do it that will work for you.