Equalization : using the spectral or the temporal signal?
If you are trying to make a proper filter, you would want to use FFT convolution, which is like OLA, but not the same.  OLA is more of a synthesis technique for reducing noise between frames caused by incoherent phase mangling from directly manipulating frequency data.
You also need to resolve the phase of the bins for your filter.  You are only defining the magnitudes and phase at those discrete frequencies, not the frequencies in between, which can be radically different then what you have in your head.  The easiest thing to do is to use linear phase to center the impulse of the filter in the window.  This can be done by multiplying each bin magnitude by e^jpik.
If you are trying to realize an analog prototype, this is a bad way to do it.  Your frequency bins are linearly spaced, but analog filters are logarithmic.  The effect will be that your lower bands have a lower “Q” and vice versa.  You can still do it, but it may not do what you wanted.