Most of my human pupils come to me from one school of equitation or another, whether they realize it or not.
Those with a Western or colonial stock-style background are using essentially no contact (at least when they have the luxury of an arena).
Those with a “Dressage” frame of reference have – almost without exception – inadvertently internalized Prussian conscript equitation so completely it will takes weeks of deprogramming to recover them!
The latter are used to holding several pounds in each hand (to hold their horse back), while (confoundingly) nagging with their legs (to keep their horse going forward – in spite of being held back), in hopes of effecting Steinbrecht’s sense of ‘appui’ – which aims to have the horse “tight as a bowstring” between the hand (“hands” in their case) and heels.
Neither is effective for (actual) high school/academic/Baucherist equitation, and, generally, unbeknownst to both types of riders, the original ideals of the equitation they think they are pursuing is actually – get this – IDENTICAL to the the equitation they disparage! I digress.
Traction should never sum to more than the amount created in gently lifting the weight of the a rein with a finger.
Within this small spectrum we have ample means of conveying our hand is “open” and/or “following” and/or “vectoring” left or right, and/or “blocking” to brake, stop, or reverse.
By default, the “0” point of pressure should be reminiscent of –
… Leading a lady onto the dance floor. A ballroom dance floor, not a mosh pit (I said a _lady_).
… When a parakeet sat on your finger
… When you realized something was nibbling your fishing line
So how much pressure is ideal?
By default, none, really.
At least, to be more technically correct, not much, and not often – and in no case pervasively.
Just enough to be “there”. Just enough to create your end of a “live” rein between momentary, fractional _+/- adjustments to effect heading, bend, speed, and collection.
When there is no reason for “traction”, there should be no traction. The horse is “at liberty on parole”, as long as he keeps doing the last thing he was asked to do correctly.