Yep, pretty much everything you need to know has been said. I'm a jazz player cum bluegrass player myself so "I feel ya."
KISS is the golden rule.
And watch out for those extra beats here and there, which are part and parcel of traditional BG, and still throw me for a loop. It will feel like the beat turned around. Which it did. And even though you're mostly doing Root-Five, if you play them backwards, the sky will fall!
A lot of times the music is simple enough that somebody can yell the changes or the numerals out at you while you're playing. If they time it right it should work out ok. And after a chorus or two, you've usually got it down.
Like any music, familiarity goes a long way. Listen to BG records and get comfy with the tunes.
Bill Monroe of course, and
Bluegrass Album Band
Don Reno
Jim and Jesse
Flatt & Scruggs
Alison Krauss & Union Station
Seldom Scene
Ricky Skaggs
etc