This solo database has been compiled over several years and from many different resources. Some items may not be graded, some are in two (or more) grade listings because different resources grade differently.
The book “Solos for the Student Trombonist” gives a great deal of information about many of these solos. I recommend that you get that book (second edition) and use it as a starting place.
“Solos for the Student Trombonist” has an excellent list of recordings in the back. A great way to learn the solo repertory is to get recordings and listen to them carefully.
Of course, there is no substitute for a good teacher!
Most of the solo repertory is available from hickeys.com.