One method might be to create an adjustment layer above your text and add a blur and adjust it to taste. Then duplicate your lens flare, place it over the adjustment layer and then set the adjustment layers track matte to luma. Now when the bright spots of the lens flare move near the text, the text blurs. You could might also want to add a curves effect to your duplicate lens flare and really crush the blacks, so you only have the hot flare center and not the rings effecting the text.
Another option that also would use the adjusment layer would be to make a solid with a circular feathered mask(lens flare size) and use that as your luma/alpha matte. Then you could just alt-click your postion, use the pickwhip and tie the circle-solid to the flare center.