Using a whizz wheel with the sliding bit of metal in it, the E6B, for your wind calculations will help.
It does the ETAS calculation for you, because the lines are curved.This way it's never an extra calculation, and by always having it done, theres never a question of when you should use it, or when you should not.
You'll still need a Jeppesen CR computer for the Mach number and temperature calculations, but you can take both into the exam.
Most of the time, for some reason, doing the exact same problem on both computers will give you two answers one knot apart. That's close enough, it doesnt matter which one you use.