TMZ/Getty Composite

Sean "Diddy" Combs is using his time in jail to teach his fellow inmates business skills ... and the men who picked his brain are singing his praises to the judge who is set to hand down his sentence next week.

Diddy's legal team is giving Judge Arun Subramanian more legal homework in the form of additional support letters from dozens of men who are locked up with Diddy at MDC Brooklyn.

In the letters, included in a legal filing obtained by TMZ, the inmates say they took the Bad Boy Records founder's "Free Game With Diddy" course behind bars and learned a lot. Getty

Here's a sampling of what the jailbirds are saying:

Arturo Santiago writes, "Because of this class I have a purpose, something to look forward to every day."

Douglas Welch says, "He has sh

See Full Page