I use the E-Z Wipe product that comes packaged free with Duracoat and Apex foils. It is like a wet-nap you get in a restaurant except the solvent is 99.7% Anhydrous Isopropyl Alcohol (also called isopropynol). It works fine. You can also use the solvent itself, available at most chemical distributors, applied to a lint free cloth or paper. The main thing is to make sure it is the real deal, 99%+ anhydrous, meaning water-free.
I use "Kleen Kloths" search and you'll find a lot of places to buy them.
I get many uses out of one cloth by using it and putting it back in the pouch and sealing with a clamp/clip.
And yes, be very sure whatever you use it is pure, with no water.
No you're fine. 99% isopropyl and 99% isopropynol are pretty much the same thing. The main thing is not to use the isopropyl alcohol commonly sold as rubbing alcohol in pharmacies. It contains more water than alcohol.
I don't clean as often as I should, from memory gerber recommend every 5 metres or so and also everytime you change a foil. As Fred says use 99%+ isopropyl as any less will have water in it, what happens is the water drys up and the dirt left behind blocks the hole and you end up with a pixel wide line all along your work, and your left doing nothing but small stickers and trying to miss the line.