Instruction

While like most things, it is simply practice that is required to gain proficiency with scraping, training with experts can help in speed this learning process and provide techniques that can be more efficient than others. 

In Europe, the Lüftinger brothers with their company MASCHRATUR OG (www.maschratur.at) offer courses which I  I have taken and can recommend. This course is not inexpensive but if you are going to rebuild machines of some value they make sense.

In the UK Clive Lamb www.lambco-machinery.com/ offers scraping courses from time to time. I haven't taken them but I trust he knows what he is doing. 

I do not know of any quality instruction in the US,  I cannot recommend anything offered by Richard King, having spend my time and money on his course, I can say with confidence that the quality, approach and professionalism are severely lacking,