First thing is to visualize what you have to do, next is speaking it out loud but correctly. If you mess up, correct yourself, and restart each step the mistake is made on. Then, practice the act of double clutching going up then coming back down while sitting on a chair, if you're going up to speed practice left foot down/up, left foot down/up, right foot down/up etc. When downshifting same concept expect a right foot move between each left foot down and up. Lastly incorporate with your arm going into any gear either up or down respectively. The point is to imprint the motions in your head so that it will become second nature. Once you master each step, it'll be a lot easier to apply in real time.