brush coating your hull is not good enough

Here is an article on hull finishing  which can be summarised as follows

Quick guide:
· Any marine growth is bad news.
· Brush painted finish is not nearly smooth enough; aim for roughness height
less than a human hair.
· If sanding, work through grades to 360.
· Don’t waste time using 360 grade if you have 80 grade-sized roughness – get
rid of the big bumps before working on the little ones.