I have tried exactly this, and it does not work. Nobody who did direct work ever had recommendations for peer workers. They just don't care. Most subs work directly with generals and not each other that much.

The general contractors know which subs are (currently) good and bad, so their recs are good, but you have to be friendly with them for them to share (instead of taking the project on themselves).

Ah, that's a shame :/

Worked for me, bathroom guy recommended a carpenter that turned out great. Was hoping it was a general thing one could do.

Professionals trade favors for each other. Someone who has done good work for a peer won't necessarily do good work if hired by some rando.

The original guy’s rep is on the line for making the referral, so if there is already a relationship, he will want to rec someone who will do good work.