sounds like you pretty much did the right thing, get him thinking instead of reacting, when you get him under control with the one rein, do some more circles and some figure eights around trees beside the trails. Figure 8's especially when they have to watch out for trees seems to be more calming to them than circles. I kinda handle it like punishment and am forceful in my voice, lettign them know that spooking is BAD, I dont do the oh bo bo its ok calm down now pat pat pat,,,, I do the more NO Knock that crap off, get around that tree, There are some trainign tips you can do in the round pen that worked very well for my afraid of his own shadow horse. I back him up, then run at him waving arms, sliding lead line through my hand, as soon as he stops moving I stop. I do the same with wierd items, like plastic bag on end of stick, beer can with rocks, waving hat, As soon as his feet stop I stop.. He still gets wierd about stuff on the trail but what I have done is teach him to freeze in place. Way more safer than his old habit of rearing and Hi ho Silvering in the opposite direction over a turkey feather in the trail.