I did a walnut blasting on my car about 8 months ago in my home garage and while messy, I wouldn't say it's too hard if you've got the right tools. In the future I'd use a drop cloth and a fabbed plate to go over the intake port I'm cleaning to keep things cleaner. I'd probably be down for helping some of the locals out if I hadn't just bought a house. Maybe if people miss thread killer's trek to D-town I'll be able to clean some valves in a couple months.
As for preventing buildup in the future, There's really no way to do it 100%. Catch cans help some, but there's a debate afaik as to whether or not they place undue stress on the PCV system. Moreover even the best designed catch can will only catch blow by when the car is in boost. Otherwise the vapors are redirected through the internal PCV system's separators and then right back down into the intake ports, bypassing any catch can you'd have installed. I'd say regular (every 40-50k ) valve cleanings are probably the best solution at this point. Sucks, but that's how it goes.