use sand paper, it will damage the surface). I use a water borne urathane primer ( let dry over night). Then I use a water borne urathane finish (I like to use the satin finish). The finish has a 72 hour curing time, It is time consuming, but you will love the finish product.

kilz oil based primer/sealer will cover it.(it looks like it will leave an imprint of the piant thickness.) If it is a latex paint you can use goof off to remove it, then kilz.