I use a razor, but make sure you hold it flat on the glass or you will scratch it. If you let it build up to thick,it will be harder to get off. I do mine about twice a month.
My only exprience with an acrylic tank however, is a FO system and theirs does not grow any coralline...but their acrylic blade is great for all the spiffy green algae that grows in that tank
For glass, the stainless steel blades are great, and they make several different handles. I've got a 24" handle and a hand held handle, and the blades fit both. Blades and handles are interchangeable.
I second the credit card technique. I use it on my tank for the corraline and for getting the algea at the very bottom of the glass at the substrate level.
What sucks is, the more you scrape the more it appears. At least that is what happens on my tanks.