Does anyone here use long johns as under armor? If so, how does it work. I know it keeps you warm (i wear it almost everyday under my dress shirts in the winter,) but how does it wick? TIA

use it over my bibs for winter riding and no problems.

Just remember the BOTTOM line regardless of what you use....
Nothing gets between your arse and your chamois!

thanks, how about the pants. would over my shorts, but under my tights work too. If it works, I just can't see myself paying the price for the riding specific long underwear when these are like 5 bucks at target.

I would try that....sure.
It's all about layering whatever....

I'd go chamois/shorts or bibs, whatever you prefer (I'm a bib guy).....
Then go your under layer....
Then go with a wind pant full length pants over the top.

It'd probably be fine for shorter/less intense distances, but aren't most long johns made out of cotton? Cotton isn't that great at wicking away moisture --- so if you used it on long, sweaty rides, you you be asking for some cold and discomfort.

Yeah....
If you don't want cycling specific....check some of the sale rack stuff in an area of running clothes too...a basic running tight can work nicely at a little less cost.