i agree with what the guys are saying , try and hold him as if when your putting the tack on .. other then that dont smack him in the nose , otherwise he'll go headshy ..

http://www.youtube.com/watch?v=2eDsIiBVuuw
watch .. XD pretty neat !

i used to have a horse with a pink nose with the same problem, she was headshy anyway because her previous owners had hit her, so i don't reccomend this. if i wanted to put suncream on her nose i just stood next to her on her left with a handfull of hay (or pony nuts) in my right hand and densly covered my left palm with suncream as she ate the hay i quickly, but gently, wiped her nose with my hand, and before she could realise i'd done it she was all suncreamed up, and even if it's not completely rubbed in your horse will still be protected. It does make a mess of your hand, but it works. and you probably already know this but use a really high factor suncream or just use sunblock. Hope this helps x

i'd agree smacking will prob make him worse-either wrap your arm round his head like your tacking up (if that makes sense?) or maybe consider buying a nose guard??these are a UV protecting piece of fabric that attaches to the nose bit of the headcollar-protecting the nose from the harmful rays of the sun-theyre only about £15ish but must be used with a fieldsafe headcollar so if he gets stuck it snaps-might be an idea if he's that bad??