Hi Carrie, from us we have a product Power clean - this can be diluted 1-20 and the sink cleaned over , leave the sink 3-4 days after this to dry fully or until all moisture has released.
after this use a suitable impregnator - we have MN stain stop.
apply saturate and remove all excess -buff fully dry
maintain after this with lithofin Easy Clean and when required -use the diluted power clean for a deeper clean or to remove salt traces.
deep clean and re-seal every 1-11/2 years to keep on top of it -
don't - leave soap or water on the top to dry out -try to remove these after every use.