Speaking as a hardened luddite, I find SkyDemon light and AirboxArare to be the work of the Devil but then he has all the best tunes
. This is what you will use once qualified and be glad it exists. Until then, A pad of paper, a cheap whizz wheel and a head full of random numbers, a ruler and protractor and some time. Spend a couple of weeks thinking of three numbers and doing the triangles with ruler and protractor.
Check them with the whizzwheel until they always match. Then you have both ways and the Nav exam will be a doddle.