Expat - here's how I use equalizer ....
If you touch one of the 'spots', it is highlighted, and then the freq, =/- dB, and Q appear at the top of the screen. If you them touch the actual freq (eg 40 Hz), you get a keyboard pop up, and you can then key in the exact freq you want the spot to apply to.
Do the same with the +/- dB once you have the freq set, and then you can very precisely set the required eq level.
With the Q, this seems to set the width of the band - so you can make it narrow or wide - at least I think this is what it does.
Using these manual inputs for each 'spot', you can very precisely set up a full eq.
I think it's one of the huge benefits of Equalizer over Equ. The one thing I'd love to see Equalizer do (that Equ does) is to be able to set up a full eq scenario, then raise or lower the entire preset spectrum (rather than doing it manually).
Am enjoying both apps immensely though

Equ is 'fun' to play around with - but I find that Equalizer allows me to get the results I want quicker and more accurately.