Matthew, you are a bit cynical, one could if gifted with memory learn all the declensions of Latin without a course. There are only 5 declensions x 5 cases x 2 numbers (sing. +pl.) and the more useful ones could be focused on. Besides, for names one wouldn’t need to learn the plural.
1st decl.–most women’s names–those ending in --y in Eng. or --a
(BTW, I think Thomas is declined like this–Thomas, Thomae, Thomae, Thomam, Thoma.)
Mariae (of Mary)
Mariae (to or for Mary)
Mariam (Mary–as a direct object–like ‘Amo Mariam’, I love Mary)
Maria (by Mary, with Mary)
O Maria! (O Mary!)
Also ‘Sancta,’ Saint if it is a woman, is the same, Sancta, Sanctae, Sanctae, Sanctam, Sancta, O Sancta.
2nd Decl.–many men’s names especially non-Hebrew ones: Roman or Romanized names–Petrus, Paulus, Iacobus, Matthaeus…
Most names ending in US will be here–but some aren’t–ex. Jesus is declined as 5th decl. I think.
Pauli (of Paul)
Paulo (to or for Paul)
Paulum (Paul as a direct object)
Paulo (by Paul, with Paul)
O Paule! (O Paul)
Also you use this 2nd decl. for the Masculine form of Saint: Sanctus, Sancti, Sancto, Sanctum, Sancto, O Sancte!
3rd Decl.–I think a lot of Hebrew names come in here–Michael Michaelis Michaeli… etc., and so on.