I learned how to fly fish on the Hex, and there is nothing quite like it. It will drive you crazy, as it happens heavy on some nights but not on others, and not every stream has them (e.g., nothing on the Rifle). The best way to predict when it is going to happen is to watch for hatching on area lakes (e.g., for the Maple River in northern lower MI, Burt Lake is a great predictor, especially at Hoppie's Bar on East Burt Lake Road). You can count on the first stream hatches about a week later.
If you want to fish at night, LEARN THE WATER during daylight hours so you have a pretty good idea of where everything is (holes, logs, rocks, overhanging shrubs, etc.) before you go out there and trip or snag or kill yourself in the darkness. CARRY A FLASHLIGHT!!! Get there before the hatch comes off - in northern lower MI this is around 10:00 p.m. - and get yourself into a stretch of the river where you feel comfortable casting and know you won't just be putting your backcast right into the trees/shrubs/grass behind you. Relax as it's getting dark and scout locations where you think fish will be rising, generally a few feet out from close cover - logs, overhanging trees or shrubs, deep holes, or deep banks near grassy edges. These are where fish will establish their feeding lanes once darkness sets in and the insects come floating down the water. When it begins to happen, you will know - there is NOTHING subtle about it.
WHY fish the Hex hatch? Because the fish go INSANE. They will literally run into your leg and rise within an arm's length of you. EVERY fish on the stream will be feeding on them - big ones, little ones, and everything in between. You would never believe the stream holds that many fish if you stick to daylight hatches. On some nights the water seems to be literally boiling with fish. The little guys make little splashes; the medium-sized ones make big splashes; and the big boys just suck them off the top with a "gloop". Fish as late as you can, because the little guys fill up first whereas the bigger ones have to feed for longer to get their fill. And, I have heard, the real monsters actually target the little guys (like the brookies) because they are so distracted by the feeding frenzy they never see the jaws of death coming at them from below...
To be honest, I didn't do a whole lot of DAYLIGHT fishing for many years because, well, I felt too OBVIOUS. Geez, in that crystal-clear water I felt like every trout in the stream could see me coming while the sun was up! This is one of the biggest advantages to night fishing - less visibility, plus fish are braver and will feed farther out from cover (and away from potential snags). You can use heavier tippets (you will want to with bigger flies) and your presentations can be less precise, both because fish care less about a little sloppiness and will move farther to hit a fly.
I have done my best fishing for trout after dark, on many other hatches besides the Hex and with attractors when no hatches are happening. A size 10 White Wulff or Royal Wulff works wonders after dark and both are easy to see with their white wings. A cricket or katydid imititation can be a killer too since these insects are largely active at night. (Tie a hopper pattern in black with gray wings for a cricket, and in all green for a katydid.) Even when vision fades, you can hear and feel what's happening out there if you pay attention. And like I said, bring a flashlight because you are going to want to change flies, pull them out of streamside vegetation or logs, and it sure help when unhooking fish and finding your way back to the car. DON'T BRING A REALLY BRIGHT ONE or every fish will really see you coming.
I love night fishing, and not just for the trout. A whole different community of wildlife emerges after dark, and you'll hear them all around you. If you are afraid of the dark, I don't recommend this as you will hear things that will make you sh*t your waders!! E.g., screaming owls, beavers slapping their tails, and large mammals walking around on the banks. If you are not intimidated, however, there are LOADS of trout out there that you will never, ever see during daylight. BTW, bass will feed after dark, too.
Good luck, tight lines, and heavy hatches!
No matter how big the one you just caught is, there's always a bigger one out there somewhere...