Did he design your sets? Give him "Sets Designed by" credit.
Did he do the costumes and make-up even thought he doesn't
have too much knowledge?
Or you could ask him what credit he would like...
There isn't a "higher" title - both are important and essentialNo he won't do costume and make up. Only prop master/set designer as of now - kind of wanna give him a higher title but not sure which one.