Guide me through valve clearance setting!

Bit of an amateur when it comes to this!

I lost my feeler gauge so bought a new one today. It's on a Skoda 1.3 Spi engine, which could definitely do with a bit of adjusting!

I have the eight valves 1 - 8,

I understand these principles:
'Rule of 9' (ie when valve 8 is fully open then you adjust valve 1, valve 5 open, then valve 4, etc),
When a valve is open, the spring is in a compressed state,
Feeler gauge will feel 'sticky' between the rocker and the valve as if there is some 'drag', but not enough to hold it in place,
I put the car in gear and push it forwards and backward to open/close the valves.

I don't totally understand was is truly 'open' though? Can this really be judged just by looking at the spring in the suspended state between 'going up' and 'going back down again'? Can you check timing marks anywhere?

Is there a best way of holding the feeler gauge - is it OK to have it bent a little to clear obstacles as long as you can feel the resistance on the blade?

I've had a go at it today, but will do it correctly tomorrow now I've practised - any tips/tricks/corrections/observations, etc.

Thanks.