Sink form finishing

Building forms was a relatively quick process in comparison to finishing. I wanted to achieve as smooth surface as possible that would not require polishing later on. I knew it was possible because we have done several concrete mix tests. We were pouring them into used ice-cream plastic containers trying different proportions as well as pigments. Most of the samples replicated the smooth surface of the containers nearly perfectly.
I've decided to paint the forms to achieve a seamless shiny surface. It would have worked great had we had it powder coated or used a similar process. Instead I have tried a dozen different paints, laquers, enamels and practically stripping it and trying again each time. It was the time when we were ready to give up the idea several times and just buy a sink of the shelf. Eventually the best results I have achieved were with a spray enamel paint made for repairing old bathtubs. It left a nice glossy surface and a fairly even coverage. There were problems along the way - unintended damages, repairs, running out of paint in the middle of the process, so it took several months on and off to have the forms finally finished. Considering the amount of time we have spent on them they are probably the most expensive sinks in the world made out of the cheapest available material. A very tough learning process.
Even though the form elements were cut precisely and glued fairly well they still needed a considerable amount of spackling, sanding and then rounding the edges.

Below is a picture showing problems with painting the surface I was running into.

Here is a picture the moment when finally the spray paint started yielding good results.
And this is a picture of the guest bathroom sink covered with anti-adhesive concrete form solution and inside edges rounded by filling with smooth gray silicone.