I've had this problem since I started taking regular trips to work with my bike, from feburary to november. Summer is not a problem, but autumn and spring can be pretty rainy here in Hungary. And the rain is not your friend, when you're riding a bike. It get's on your everything, which I can cope with, because eventually it will dry over time, but the rain on the visor gets in your sight.

I've seen mikeasaurus' instructable with this idea, and basically i copied it, with some touch-ups and modifications.

List of things you'll need:

gloves (duh)
strong nylon thread (mine was a leftover from another project)
strong needle (if you're having trouble poking it through rubber then pliers, too)
one mildly used wiper blade (make sure that it's not completely aged)
an utility knife (x-acto knife/stanley knife, depending on where you live)
half an hour, depending on your skills in sewing

Step 1: Prepare Your Glove for Work

Make sure your glove is clean, and laying smoothly on your workbench. ;)

My glove has a factory default terrycloth piece on it's thumb, but hence it's useless (see caption), I wanted to preserve it's function. After all, it's still good for smearing bugs all over the visor.

Step 2: Prepare Your Wiper Blade

First, remove the wiper blade from it's housing (in my case that was accomplished simply by pushing it from the metal holders), and remove the steel brace/shank from the upper hole, as we won't be needing that.

Next, clean up the blade with some handwarm soapy water and a clean rag. Used wiper blades tend to be very dirty.

Then, cut down the upper part with your trusty utility knife (marked with a dotted green line on the picture). Depending on your skills, you can do it while holding with your other hand, or laying it down, and ruling it out with a steel ruler, and cutting beside it. I did the in-hand approach, but I'm not skilled, but lucky.

Make note the red dotted line, as this is where we're going to puncture the rubber. First, I thought that I only cut from the steel brace's housing, adding more flexibility to the blades, but the rubber was so hard to puncture with my needle, that i had to compromise.

Measure the outer side of the glove's index finger from wrist to tip, and cut up two pieces of rubber.

Step 3: Sewing

Measure the blades to the thumb piece, and, beginning with the inner blade, sew on the first one to your glove. It helps if you put something in the glove, so you won't accidentally sew it in.

Make sure the stitches are uniform and tight - but not too tight. I did mine with 5mm stitch distances.

When you're done, sew the other blade on, too. I found that it's easier to sew the outer one last.

Step 4: Finishing Touches

Make a nice knot to the end of the thread, and cut away the excess. As with cars, we don't want anything getting between the visor and the blades.

With my long double blades, i can wipe my visor with one motion, and the rubber is bendy enough to work on the left handle controls.

On a plus side, when I'm wiping I hold my hand in a thumbs up position, and other bikers think that I'm overly positive riding in rain, so they always wave back.