Personally I wouldn't put my finger anywhere near the screen - you may have been lucky and the invigilator just wasn't looking.
For the sake of a possible automatic fail I would try and do it like everyone else, safe in the knowledge that even those who pass the whole thing generally are pants at that test!
Most people I know try and remember the directions with some sort of movement and repeat it (eg tracing on the desk with your finger or moving your head (up = north right = east etc) if you constantly repeat this as you are taking in the info you overcome the 8 unrelated items limitation by practicing (all that human factors flooding back now!) and you just need to remember the 4 distances.