How can I more easily install a Nema 6-50 outlet?
You can't use that cable for a new outlet.  It needs to go to the scrapper.
You'll need to re-run it with proper wire or cable, such as 6/2 w/ ground.
Given your complaints about the stiffness of #6 wire, I'd suggest running some sort of conduit, such as &quot;smurf tube&quot;, and run individual THHN wires in the conduit.  That would do a couple of things for you.   First, you'd be able to use #8 stranded wire for 50A, since THHN is allowed a higher operating temperature.  Second, you could defer the &quot;neutral&quot; question and simply add the neutral wire later if needed.