Manny years ago I bought a tank to repair and
demonstrated the basics on you tube. There
are much better videos than the one I made.
First you need to get whatever you’re repairing
straight or flat. This includes curved surfaces.
Then you are attempting to get the surface
smooth. The closer you get to perfectly straight
and perfectly smooth the less distortion you will
see in the reflection. That is all there is to it except
it requires a lot of work. There are tools that can
make it easier. Especially a readily good buffer
but for the average hobbyist it doesn’t justify
the expense. I bought a Harbor Fright buffer that
was on sale for $40.00. Even with a 4″ X 1/2″
wheel it struggles. A good buffer from Eastwood
is $350.00. There are all kinds of videos on you
tube. Check out ” How-to & Buffing Basics
Demonstration with Eastwood” and search for
others. There is no secret. Its mostly about being
willing to spend a lot of time doing a boring
dirty job.
Tubs
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.