Yea, knowing another Slavic language definitely makes it easier, with Polish, at least you don’t have to learn how to pronounce Ы from scratch. But one being west language and the other being east can also screw you over, because many things are similar, but not quite.
Be careful not to speak only with Ukranians, they, of course, have their quirks in speaking, like using soft Г which is prevalent in Ukranian, but never used in Russian and using за instead of про in some places, for “to speak about Russian language” they would say “говорить за русский язык” instead of “говорить про русский язык”. Of course, unless you are ok with picking up these quirks.
How would one go about using that sink?