I'm gonna say that yes, you can mostly jump in to what's being published these days.

I wouldn't start with The Devil You Know, though. That's the one where you really do want to have read what's come before, even though it is a lot. This being the final cycle of BPRD means we're at a point where starting now would diminish any big moments that came before. If nothing else, I'd watch for Dark Horse digital sales. It's a cheaper way to get caught up on one million back issues of BPRD.

Most of Hellboy can be read on it's own, up until Darkness Calls/The Wild Hunt/Storm and Fury. Those omnibus would be a great way to read his main story, if you want to wait for those, though.

Hellboy and the BPRD is very new reader friendly. There's not a lot to get caught up on, either, if you wanted to do that. Though, the series is hit and miss so far. 1952 is the best so far. The stand alone issues are also good, but the multi issue arcs fall short for me after '52.

Rasputin and Koshchei can probably be read on their own, but they'll be better with previous knowledge of those characters and their relationship to the larger mythos.

They'll be released in their own Short Story Omnibus, but any and all Hellboy short stories are great and can be read any time. While they're intended as stand alone GNs, Into The Silent Sea, and especially Midnight Circus tie in to other stories, but it doesn't diminish them on their own.

That's my take. Others might have different opinions.