Almost all the rescues do not want certain parts of their body messed with. Remember that the Settle command is purely an exercise of submission. If you expect your dog to respect your authority, and more importantly, to trust you, then you must be reasonable, fair and consistent. Try to always be aware of what's going on and your surroundings, so that you can do your best to never issue commands at a moment where compliance might jeopardize the safety of your dog. If you are not willing to follow through with a command, then don't even bother saying it.
Dogs are very intelligent.
And even if they act like they don't hear you, believe me, they do, so only say something one time. Some things they will learn so quickly it will blow your mind. Other things might take a bit longer. The more times you can expose your dog to a learning exercise, the quicker they will learn. The more times your dog makes a mistake, the more chances you will have to show him the right way to do things.