I have done this multiple times, and the process is infuriating. When sending IRA funds back to my Schwab IRA, I complete Schwab's form, and upload it to Schwab, as SDIRA has told me that they can't push the funds, Schwab has to pull them. Fine. Then I spend WEEKS waiting for the transfer to complete. Even though I hound both sides of the transfer, they just point fingers at each other saying it is "their" fault for the delay.
Then, for the "privilege" of such poor service, I get a $50 fee from SDIRA for processing the disbursement. Nice.