Lyrics are very important, and sometimes they more or flows easily while shredding the guitar - and then the BIAB work starts afterwards. Most of the time I sense a mood in a song and know the lyrical direction, but finish 80% of the compositions first - then I have a few phrases or keywords that evolve from that process.
The fine tuning of the lyrics and possible corrections to the composition can be anything from a joyride to a painful process.
Do you ever go through the full process and then ending up feeling that the whole idea got lost "in translation", and then put it into the archive of songs not to publish....after 1 or 2 years you stumble across the song and know exactly what it needs to give the song a re-birth?