EQ and finding problematic frequencies

I have read other various articles and tutorials on EQ and cutting problematic frequencies when needed.
One way I have heard of doing this is to use a bell curve with the highest Q setting and sweep the range looking for them. I guess my question is what to look for when doing that. My assumption and practice recently has been doing that and finding the frequencies that have an extremley resonant (or even piercing) sound at a gain increase of like 6-9db. From there then just basically inverting the curve so that it lowers that frequency.
Am I on the right track in using this method, or should it be seen as something that can overly dull your sound? Or is it really something that you should not even try to do unless your mix sounds muddy?

I try to take my friend Michael Stavrou's advise - Don't sweep to find the frequency. Try to guess where it is and then turn the EQ on, shut it off when you're moving the frequency. This is a "better" method because over time you get better at knowing what frequency you are hearing. It takes practice like anything else, but it's great when you finally find one on the first try. And this helps in all areas of mixing, recording, of course.

But, otherwise, yes what you described also works.

Thanks for the response Brian. I come from a background of mixing vinyl so had a good general knowledge of 3 band EQ but as I am getting more into production, it obviously plays a pretty vital role and was a little thrown off by other articles I read online (which I take with a grain of salt if you know what I mean) but since my post I have been able to watch more videos from here to gain some additional knowledge and insight.
Thanks again, and really have enjoyed your TNT in live.