Are you supposed to shrug the bar up or shrug yourself down? Different coaches will say different things, but I'm sure the best ones out there all mean the same thing. Meaning they're looking to give the athlete the verbal cue that will make them move properly. I believe it's both. The shrug happens at the end of the second pull and initiates the third pull.
A lot of folks Clean or Snatch without shrugging very much. If you don't and you start it can be a game changer.
For both the clean and snatch the shrug will affect the bar path and your movement around the bar. Lack of the shrug can cause the bar to get away from you causing you to have to move forward for the reception. Shrugging will help you finish your pull and get that last 10% you need to move more efficiently.
For the Snatch the shrug shouldn't really end until the lift is completed. Lack of a shrug during the snatch will usually cause your shoulders to not be as active as they should be making the reception of the weight more difficult. If you shrug and keep the top of your scapula squeezed together (showing your armpits) for the reception you'll notice that the received weight will feel much lighter and your overhead squat position will be more comfortable.
Spotting the lack of shrug: You move forward to receive the bar Shoulders are unstable during the reception of the bar during the snatch You have tiny traps
Drills to help you shrug: Tall clean and snatches (no hips). Make sure to initiate the movement with a shrug. Clean and Snatch pulls
Same advice as last post. Put them in your warmups daily if this is a problem for you. Start with PVC, move to the bar and then do some weight. You should be able to tall snatch about 50% of your snatch. If you can't then there's a problem. You should be able to tall clean about 75% of your clean. Even if you can go heavier keep it light so you can drill daily.