For state land, I assume if it's not posted than I can hunt it. I know there are some instances where you can't hunt it or have restrictions to some parts, but like many things in WA, it isn't completely clear. Each agency (WDFW, DNR, etc) could have different rules and most are difficult to find or don't exist.
I called DNR once and the guy said go for it but also admitted he didn't know for sure one way or another and was luckily pro-hunting.
I'd be careful about postings. I know a few folks in 139 who post no trespassing on BLM land just because that land is near theirs, and they know people won't investigate.
Yeah, I mean signs obviously put up by the state. Unfortunately there are way too many no hunting signs on public land.