Viva advice is available in many forms. There are books, podcasts, blog posts, seminars and people you can ask for help. You could talk to people on the internet, in your department or from your own network. You could speak in person, over email or via Zoom.
Viva advice could cost you money to buy a book while reading a blog post could be free. Searching the internet to find help could cost you time but be very convenient; asking a colleague might cost you in terms of scheduling, but be a quick conversation at the appropriate time.
There’s lots of viva advice and it costs in different ways – but it’s only worth the cost if it helps you to do something (or perhaps not do something) that helps you on the way to your viva. Viva advice is useless if you don’t do something as a result.
Advice is valuable, but the real value comes when you do something.