On 9/19/2018 8:40 AM, George P wrote:
What's the procedure?

Seems simple but I could be missing something.
1) Turn off valve to large tank (250 gallons).
2) Open line (wearing gloves & pointing away from face)
3) Connect the small tank (20 gallons) taking care to prevent air entry

Is there more to it from a safety standpoint than that obvious procedure?

Pretty much that would be it. Assuming the fittings match. I'm not
sure what type of connector you have.