Michael, I have no problem flushing oil lines. I've got an electric pump that will push about 20 GPM of filtered mineral spirits through them. After about five minutes of that, I hang them to drip dry, and then chase them with lacquer thinner. I then blow them out, directing the exhaust air into a clean paper towel. If nothing dirties the towel, I figure I'm good to go.
An oil line or hose doesn't have all the little nooks and crannies for crap to hide in like a cooler does. When cleaning everything, don't forget the Accusump valve, and the check valve.
On mine, I only have about 2 feet of hose that sees unfiltered oil.
Jeff