When it comes to completing DLC 1 off-duty (Army Reserves), how does one go about getting paid for it?

You will submit a signed 1380 for the training along with the certificate of completion to your S1 to be processed for Pay. IOT properly have the 1380 filled out, speak with your S1 to know what to fill in where. The person that signs the 1380 would be your Commander or anyone in the unit that has Signature Authority for the Commander for such forms.

See the FY23 poliy dated 1 DEC 22. You need a CMD counseling, completed DA Form 1380, and completion certificate. https://www.milsuite.mil/book/docs/DOC-1218752