Dumb question regarding scrapers.....and scratches

[sphelps]

I personally just used disposable razor blades from HD ($10 for 1000) and my hand.
Problem is you need to replace blades often to avoid scratches and using brands specific to aquariums can get expensive. You could also try the plastic version which is made for acrylic, you won't be able to scratch the glass with it but it will be harder to use.
I don't think there's a big secret to it, just common sense and attention to detail. Others might be able to recomend other products but I don't think anything is full proof.