i usually play with an EQ boost with a very high Q coefficient and i look for ringing freq.. but sometimes when i cut this frequency, my sound lost power and body..
Dont' cut too much. When you've found an annoying ringing the instinct is to obliterate it with the full negative gain power your eq can muster. But by doing that you end up removing more than you want, including some needed tone. Use your ears, and gently reduce the gain until the annoying sound just about can't be heard anymore. Then un-solo the channel and listen to the mix again. If it's too thin, start raising the gain of the band until it's no longer too thin.
If at this point the ringing is audible in the full mix, your sound needs to be either replace or layered with something else that can cover the spectrum area where the ringing occurs.
Don't just EQ sounds individually.
Adjust your EQ, then see how it sounds as part of the mix as well as by itself. You can cut a lot more than you would think sometimes, especially when highpassing...
I prefer doing this while listening to the full mix. Just activate a high pass filter on your eq, and start increasing the frequency slowly until whatever you are eqing loses its tone/starts to sound (too) thin. Then just decrease the frequency a bit, and you're pretty much done.
Fabfilter Q has an absolutely brilliant feature where you can solo an eq band (click and hold the headphone icon in the band popup). In the case of soloing a high pass (low cut) band, Q will apply a low pass filter so that you hear what the cut filter is removing. That way you can listen to what you are taking away, which is very useful when high passing. Used in combination with the built in spectrum analyzer it's an extremely powerful tool for finding the right high pass frequency fast. This especially goes for things like high passing a kick, where your speakers/room might make it hard to do it by ear.
A spectrum analyzer really helps. It can show where all the sounds are fitting. At about mixdown, I generally solo each part and check where it's at on the analyzer to make sure it fits right (however, the spec analyzer can also be quite deceiving at times, so I don't rely on it).
If you don't already use Voxengo SPAN, start doing so. It's free, and it's great!