[Wire Fox]

Reviving this because there's a product just for this kind of thing. The FLSBAN by S.U.R.&R. AUTO PARTS INC. is a spring-loaded clamp assembly that's meant to plug banjo bolts. It's less than $10 from Grainger and I also saw it listen on Napa's website. I attached a PDF that has a few images of it and its variations in use. I haven't used one myself, but it looks like something I'm going to get soon for how often I work on brakes and how much I hate to work around a caliper being hung up on the suspension.

 

[Wire Fox]

I guess this is good if you have other vehicles, but this looks like it would be useless for a Dart, which does not use banjo bolts. My brake lines didn't drip more than a few drops when I removed my rear calipers using the exact method described by @Bullfrog. I used a rigid vacuum extension to press the seat into the brake pedal to keep the brakes applied.

Whoops! I've been working on so many cars lately with banjo bolts that I forgot the dart was different. You should still be able to use the other tools in the series, the FLS516, FLS38, or FLS12 (I haven't taken any effort to know what the size is of the fitting to know which of those is most appropriate for the Dart). These other ones are designed to clip onto the end of a flared fitting and seal it.