Start here then, when he reacts to something and you happen to have 10 minutes to work with him, grab some super yummy treats, I mean suuppppper yummy, stuff he doesn't get just for sitting, I like cheese or liver for this. Hold the treat in your closed hand and let him sniff it until he gets his big slobbering tongue trying to get into your closed hand, then pick up the object, allow him to actually get a piece of the food....move the object, allow him to get at another little piece....touch him with the object, another tiny tidbit, stroke his sides with the object (not over his back or head!!!), more tidbits. If you can swing that in the first try, stop there, if he really balks at any other part, take a step back, reward then end it happy.
Once he will tolerate all those things start stroking under his chin with the offending object, treat, belly, treat, legs, treat, bum, treat, rest it on his back, treat, stroke his back, treat, slowly move towards his head.
This should take at least a month, so don't try to do it all in one day but do it in that order. Everytime he flips about one step and doens't recover within 20 seconds, move back a step.
In about 8 weeks the problem should be basically gone with the exception of the odd freak out that hopefully he recovers from quickly.