I had this work with one of my horses. It didn't work with the other one I had later that was a bear to bridle.
I put a dab of spun honey on the bit. His stomach won out over his resistance to being bridled, and he started smacking and chewing as soon as he saw me come up with the bridle. It only took a few days before he was better. I'd bridle him, then take it off and put him away, in case he was making the association that bridle = work. Every now and then after that I'd randomly put the spun honey on the bit, and he became a dream to work with.
But, as I said, this didn't work with another horse, so it all depends on the individual.
I ride a horse who is VERY HARD to bridle. He has fungus in his ears and hates to have them touched. If you get the bridle close to his ears he rears up and he even flipped over once . When I bridle him I put both cheek pieces on the bottom hole so I can pull the bridle over his ears without touching them. I back him up so his butt is against the wall and stand on a stool and hold a treat in my left hand (the hand holding the bit). I coax his head down with the treat and whip the bridle over his ears while being careful not to touch them. Then I re-adjust the cheek pieces and give him a ton of treats if he was good. His bit gets gunky but it is totally worth it. After a few months of this he hardly gives me any trouble.
Looking back on this thread, it seems that bribing with food has its place. Use with caution, as with the others.
Another that caught my eye was this, if he's tossing his head or trying to get away when bridling:
"After ruling out any physical problems, I got a length of fairly thin cotton rope. Then I constructed a "war bridle" as I had been taught by an old horseman. Basically it worked like a stabelizer or "Be Nice" halter. I made a small loop in the end with a bowline knot. That end was hanging down on his left side with the line going over the poll. The line is then looped or tied like a cavesson and the end goes through the first loop. Now you can gently tug on the end of the line and create poll pressure. I tried it on him and used short tugs to get him to realize that he could drop his head down to relieve the uncomfortable feeling. Then I would adjust the bridle a little more loosely and bridle him right over. You use gentle tugs on the rope to keep the head down. It took a while at first, but rapidly improved.The rope can then be removed and the bridle adjusted."
As for me, it seems that my horse just didn't want to see the bit. It took a long time to figure it out, but to this day, if the bit is in his line of sight he tries to get away. No problem at all if I just bring the bridle up from under his nose and slide the bit in. Can't hurt to try, I suppose.