Hey Bat-Fly, for this time of year, Blue Winged Olives are a good bet on cloudy days, and we have had plenty of those lately. Also RS2’s are a good as well. Also a Vis-a-Dun works good.
Midges, lots of midges sizes 18-22. Being new to dry fly fishing I’ll give you a few examples of some midges.
1. Griffiths Gnat ( one of my favorites )
3. Mercury midge
The Black Beauty and Mercury Midge I would fish them in slower moving water. They are not really dry flies per say, but if it floats, just as good in my book, though not classified as dry fly. The Griffiths Gnat, you can fish that in a little faster water.
On warmer days, if you see a hatch, and a hatch are insects coming from the water and flying around. You will notice this more and more. You’ll see them and wonder where the heck they’re coming from. They come from the water. So try to catch one, and do your best to match it with a fly in your box. One of our favorite flies is the Adams, and it will match many different insects.
I remember on one of your posts saying you have the Cabela’s CGR. That rod would be fine on the Big Thompson. It actually should be a blast with those fish.