i degrease everything first. I get the chain lube off of the chain and wheels with a spray and a weelcheaning brush scrubber with a handle. I roll it some to make sure i get all of the wheels and chain.
I then use a mild simple green solution. and scrub by hand or with a brush.
after that i use a mild soapy water to get the simple green off and wash with a low pressure sprayer. I start it immediately after spraying it and dry with it running to make sure the water doesn't pentrate anything it isn't supposed to.
I have never covered anything...and it hasn't hurt anything yet.