I would even go so far as to bang pots and pans at feeding time...little by little of course...and reward with supper. clap your hands and then call him and play with him. What AK advised is tried and true. Associate the report with play, fun, reward, and pleasing you. I too find it hard to think a flat coat would be genetically gunshy
good luck, and please post yer progress....here's my 18 month German Shorthair, Daisy, a hunting fool!