An electrician's deburring tool (Sears) works wells for getting rid of the nasty edges on metal tubes. I also recommend getting a small T-handle taper reamer (available @ most hardware stores) for rounding up tube holes and tweaking them to size.
You might try wrapping a wooden dowl (or even a round handle from a kitchen utensil) with sandpaper. Slide it in and out of the whistle to clean the holes.
Thanks for the advice everyone. I picked up a blade hobby knife set with numerous different blades and all kinds of other goodies, 400 grit wet and dry sandpaper, and a file set. I tweaked yp my Low D and I made another whistle but I failed. Was going for Bb but it's more like an A but I am sure it is pretty much unplayable being so far off. It happens I suppose. I plan to make more, hopefully figuring out how to make them tuneable as well.
"The death of beauty is just not possible even amongst all of the ugliness that is and can be."
"Knowing how" isn't the problem. I know how, and if I didn't, there are instructions on Snr Gonzato's page. Being "as mean as get out" (as they say een mai contree) it's finding the ready-made tubing that fits even approximately snugly inside the 15mm and 22mm pipes available. Not that I've been looking desperately hard...
To remove the lettering and make all sanding,tonehole interiors and the labium ramp smooth and glossy use "Fingernail Polish Remover", otherwise known as Actone. Use a cotton rag for cleaning/polishing and Q-Tips for small areas like toneholes. Keep these wet all the time or they will stick to the PVC. Soaking the end of the whistle in Acetone will soften the PVC so you can Flare the bottom into a "Bell". this will harden as it dries out. Don't flare the Bell too much or the Bellnote will be too sharp.
"The difference between Genius and stupidity, is that Genius has its limits" (Albert Einstein) thomashastay@yahoo.com