It's not complicated in the slightest
It's just the same as you planning your usual route at the start, although you're doing it for a few more headings...
Completely takes away the guesswork of the whole thing.
Ok, I have to divert. The map says I need to go a heading of 330°. Let's see... the windstar says that if I want to go 330 I ACTUALLY need to go 315. And my ground speed for 330° is now 70kts.
And as it's 20nm away I'll be there in 17 mins.
Really easy, because you've prepped beforehand and are just reading it off a sheet. One less calculation to worry about when you're stressing in the middle of your test!