is there any thing I can use to coat the inside of the wheels behind the spokes to help wash off the brake dust without fitting my fat hands behind the spokes and scrubbing?

A friend of mine several years ago, said he always coated his wheels with liquid glass or something like that from AutoZone and that the brake dust would just wash off with a hosing when he washed his car.

Any thoughts/suggestions??

 

Hmnn the Chemical Guys wheel sealant works alright
Get an EZ brush that helps to clean the barrels

 

If you can, before mounting the wheels, give them a coat of Poorboys Wheel Sealant. This really helps when it comes time to clean them! Brake dust and road grime wash off considerably easier. I've used this countless times on both the street and track wheels and I reapply about 3-4x a year.
I also tried Optimum OptiSeal on my oem m3 rims and optiseal held up extremely well as a wheel sealant. I was able to wash about a 6k mile road trip worth of brake dust off w/ only soapy water mixed w/ a small amount of all purpose cleaner
http://www.glimmerglassdetailing.com/wheelsealant1.html
http://www.glimmerglassdetailing.com/optiseal.html

As for reaching the inside of the rim, the ez detail brush, as lexusscturbo mentioned, is perfect. I wouldnt be without one!
http://www.glimmerglassdetailing.com/ezdetailbrush.html
a brush like the zymol wheel brush can also help clean areas around the lug nuts, etc.
http://www.glimmerglassdetailing.com/zywhbr.html