I've done a brake line tuck on my Civic, I used braided stainless steel lines for the front brake lines and the ones coming off the prop valve to the rear brake lines. I was just wondering what is the proper way to get the -3 AN fittings together with the hardline? Can I just get a fitting and flare it on the hardline and screw it into my AN fitting?

 

yup

 

or get a fitting for the braided that matches the hardline

 

You could use an AN3 to AN3 union and just use a flare nut and sleeve on the hardline. Make sure you use a 37 degree SINGLE flare, not a 45 degree double flare like most brake lines.