Muscle-Up Progressions
For most people, muscle ups are a medium to long-term skill in terms of the time it'll take to learn. Perfecting any gymnastics movement requires long-term commitment and consistent skill repetition, but muscle ups can be especially frustrating because they typically can't be performed at all when you first start doing them. So rather than spending all your time on the rings trying, and failing, at muscle ups, invest some time on a consistent basis performing these progressions.
Skin the cat hand and swing
This skill is primarily to strengthen the shoulders. Performing a muscle up will entail very high intensity movement centred around the shoulders, and the shoulder girdle will be placed under strain at the limit of your flexibility. This skill builds the capacity of your shoulders to handle this strain. Start very slow and lower down through the 2nd and 3rd picture very slowly. If you need to let go and land on your feet do so, but the goal is to return back up to and inverted hand and come back the way you came up.
Once you've achieved some proficiency with this and have strengthened your shoulders sufficiently, you can go to a straight leg and, and can even work on flexing the posterior muscles towards a lever position, as shown below.
Dip Swings
