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Yes, I think that's the only way.
You registered here nearly 6 years ago, so you might not be surprised that someone would suggest there are two ways.
Responders will teach you to fish ... or to give you a fish. By teaching, the responses will try to guide through a self-learning process which will increase the ability to problem-solve the next mystery stamp. The gift of an answer tends not to do that as well. You have now received answers based on both of those general philosophies. I regularly do both, depending on the item, etc.
I agree with ZebraMan's anaylsis and it is a good jumping-off point to use in reexamining your stamps to see if you agree disagree or have follow-up discussion to clarify any uncertain points. Some grills can be very faint, so it is possible to miss them in a scan. Good luck!