Judging from your 3rd picture (on right) you have a lot of gel coat damage, stress cracking. Those fine lines and star cracks will just re-appear through any paint that you apply. You might also find that moisture has penetrated into the structure beneath the surface in these areas.
To carry out a proper repair the old gel coat needs to be removed in those areas, any damage to the CSM needs to be rectified or strengthened and Flow coat applied to build up the surface again.
If you are going to paint or flow coat the whole hull I would sand the surface rather than using cleaner. To flow coat you would need to sand down anyway to give a surface for the flow coat to grip to so you might as well get stuck in now and get the 80's grit out! Don't be tempted to use car body filler to repair hull damage, it will just not last.
If you look at my Searider 5.4 project thread you will get the idea of the work that is often required.