The scaling tool does a great job of getting you into the ballpark, if you are using an accurate equipment profile for the larger equipment.
I find that grain percentages are the most accurate way to scale. For hops, I go for the anticipated IBU contribution first, then sort of intuition for late kettle and dry hop additions. Those don't scale very well, since you usually need a lot less per gallon, than on homebrew sized batches, for the same impact.