1000 Life Hacks -- I love these tips! "Rubbing alcohol will remove pen marks & ink stains from pretty much anything." Someone else added: "It will also remove dried paint from wood floors and counter tops."
"Farmhouse Table" Used gel varnish remover to strip off most of the varnish. Barn wood look came from varnish not being fully removed; whatever is left behind will appear lighter when a dark stain is applied. Heavily sand areas that you prefer to look darker.
Just create your own sink cover by using a cardboard template and make from wood. Measure, template, cut, sand, finish, DONE. Better yet, instead of finishing with stain and/or varnish, use a food safe cutting board oil to make it a productive cover that doubles as a cutting board.