There are desirable outcomes for viva prep but lots of paths that could lead to those outcomes. Strategy is an overall type of activity that helps a candidate; tactics are the many approaches that could help someone. Effectiveness depends on time available, the preferences of the candidate and many other factors.
For example, a desirable outcome for the viva is that a candidate has a clear enough picture of their research in their mind: not photographic recall, just a good feel for the flow of the work they’ve presented.
A simple strategy for this would be for a candidate to take time to read their thesis and refresh their memory. Possible tactics – again, influenced by different factors – could be to find an afternoon to read the thesis in one sitting. Or to read one chapter per evening. Or for a certain time each day. Or to focus on particular aspects in order.
When someone tells you a precise way to prepare it might not be right for you. They’re usually describing tactics that may help with good intentions. Behind the tactics will be a strategy that almost certainly will help, leading to an outcome that you need. If some tactics don’t sound quite right for you, then listen for the strategy.
If you know the strategy you need, consider what tactics will help you best. How will you organise yourself? What particular help do you need?