bending 5/16 parts store steel line

If you go with Stainless- Just buy the pre bent, it's not worth the time/hassle of bending your own with cheap tools.
Go with the Nickel Copper line if you want to save money and bend it yourself.
Flaring the Nickel Copper line is the issue with it, if you're going to screw up/split a few end flares before you get it right. Bends are no problem.
1.Center the flair tool on the tube,
2. don't overtighten
3. don't overtighten
4. don't overtighten. You're better off to go too little then have to go more than too tight and split the tube, cut the end off and reflare.
ask me how I know... Fuel lines,brake lines (manual 4 wheel Disc, not power assisted due to pressure limits for the nickel copper line that I bought online in 2018), and trans lines all Nickel copper on all my vehicles.