In doing cultured marble tops/sinks, removing plumbing hardware is critical whether replacing or not. If you tape up, chances are there will be some peeling down the road directly adjacent to the fittings!
Cultured prep is cleaning/ wet sanding and silicone removal. Taking air and blowing several times for dust particles to settle. Also vacuuming to achieve a dust free environment and a solution of lacquer thinner and water will clean oils off surface.
Glazing the sinks at end of prep day taping with automotive pin stripping tape. Next morning tape up sinks and do vanity top with stonefleck of your choice. We can also do a solid two tone. Just pick out any swatch, and we send to Chicago for matching.