Blind casting is just nymph fishing without the bobber.

 I've been "blind casting" for more than 65 years. When I started out in my Dad's hip boots cut off at the knees no one told me to just cast at rising fish. The only advice I ever remember getting was from a friend of my father, Roy Ryan who stood on the bank watching me and hollered "Never saw anyone yet catching a fish while he was waving the G-- D--- fly around in the air".  The advice sank in, anyone who has watched me fish knows I make very few false casts and the fly is ALWAYS in the water.

Blind casting (prospecting if you will) puts the fly in play. You will never catch a fish standing with your rod over your shoulder waiting for a rise.  Fish have to do three things, avoid predators, eat and reproduce.  If they don't know you are there and it's not spawning time you have a chance.

What exactly is blind casting?  It is casting your fly on water undisturbed by a rise in hopes of enticing a fish to eat it.  Just last year I was fishing with a Florida friend who could cast a fly fairly well and did hook and land several big river rainbows.  We were on the WB in the evening and the fish hadn't yet started to rise. He was blind casting per my instructions and was having no success. After I had hooked several fish he reeled in, walked over and said how come you're catching fish and I'm not.  Was never asked that question before and my answer surprised me. 

I told him he was just casting to the water (to which he agreed) while every cast I made was to a place I believed held a fish. Went on to tell him that I had fished there many times before and knew where the fish were most apt to be.  Also pointed out the type of water that was most likely to have fish.  He  shook his head and said he just wanted to watch.

So if you are thinking about "blind casting" what do you need to know to have a chance at success. Here is a list of things worth your consideration.

1- Start out in a place where you have seen fish rising and cast to those places, the fish are there and they will see your fly.

2- You never know when a fish will eat so you need to maintain good control of your line at all times so that setting the hook is not a problem.

3- When the cast starts to move faster than the bubbles pick it up, fish that aren't rising are spooked by a dragging fly just as much as the risers.

4- Fish seek a comfortable current level, if one fish comes to your fly, there are probably more in that area,  spend a little time there and cover the likely fish holding spots.

5- Fish want to be where they can get concentrations of food without expending a lot of energy, think seams where two currents come together.

6- Fish both edges of the obstructed water behind large rocks.

7- Fish faults in the stream bottom where fish can effortlessly lay and wait for the current to bring them food.

8- Throw at the bubble lines, food get concentrated there just like the bubbles and the fish know it.

Blind casting like everything else involves learning. You are not likely to hook ten fish the first time you try it.  But you will get satisfaction when you land the first one that wasn't rising and if you keep at it you will get better and hook more fish.

After all you are just doing what nymphers do without having to tie on a bobber.