Very simple, yet effective. Gain riding skill to 100 and good quickness gains with this trick. First find a nice hiding place. Hop on your favorite mount and simply spin. (obviously, do this by applying weight to your 'A' or 'D' keys, or use a macro).
Yes, it is the sit and spin method for quickly and silently gaining skills
I used this to crank my quickness out of this world and I never lost a mount.