Currently, there are two ways you can allow Smeargle to learn those moves: Sketching the move from a Wild Smeargle that you allow it to sketch the move of your choice or Sketching the move through a Double Battle. For the first method, I recommend reading this thread where Gutten_Tag posted an example of how he does it -> Smeargle Learn Attacks?. For the second method, the only repeatable double battle currently is the Couple at the Grand Hall, which can be found on Sundays. From there, its pretty much the same as Gutten_Tag explained, but instead you would have Smeargle and the mon of that has the move you want to learn as its partner. Then, allow the mon to use the move and Smeargle sketch it (make sure your Smeargle goes after the other mon so it doesn't waste its Sketch move). If you want a more-detailed example of this process, let me know so I can do so.
Anyways, my current moveset for my Mamoswine is Ice Shard, Icicle Spear, EQ, and Freeze-Dry. You could always try to get Rock Slide or Icicle Crash on it as well through Smeargle as well.