Originally Posted by Polaris OBark

I understand that this isn't the advice you want to hear, but the best thing I ever did was replace Avid Juicys on two bikes with Shimano XT.

Unless you don't have the ports fully open at both ends, what you are describing is a clogged brake line. The caliper end is most likely the culprit, if it isn't a clog. What you don't want happening is having the syringe hose pop off, spraying everything with DOT fluid. At least if Shimano mineral oil sprays in your face, it isn't an immediate threat to your skin or eyes. (Always wear safety glasses for this kind of thing.)