How to Assess the Feel of a Bit
If you wrap a bit around your bare upper arm and take up a contact or a pull similar to those aids you would give down the rein, you will have some idea of how the bit feels in the mouth and which pressure points it is using.
If you are employing a dressage legal snaffle and you are looking for a soft consistent contact, the mouthpiece should be extremely comfortable and very smoothly contoured. For instance, with the French Link, you will feel the underside of the rings that join the arms to the plate. Indeed when you look at your arm you will see the blood loss in that area caused by the pressure.
Please bear in mind how much more sensitive the tongue is as opposed to your upper arm and how long the bit is employed for. If the bit causes pain and/or discomfort, remember, without comfort there is no harmonious communication.