After I discovered Swagelok / Ridgid roller benders and Mastercool / SURR hydraulic flaring tools there's nothing else I'd ever use. It's an investment in tools but I've never regretted using nice tools. Spent 24years making brake, fuel, trans lines with screw type flare tools and dreading it. These tools make it fun.
https://www.amazon.com/MASTERCOOL-72475-PRC-Universal-Hydraulic-Flaring/dp/B01NCYKQSNhttps://www.amazon.com/3M-Auto-Parts-PFT409-Fittings/dp/B0792KXDP9/ref=sr_1_7?keywords=sur%26r+flaring+tool&qid=1659050950&sprefix=sur%26r+fla%2Caps%2C129&sr=8-7
https://www.amazon.com/Handheld-Straightener-Portable-Universal-Straightening/dp/B09ZQY6RG9/ref=sr_1_5?keywords=3%2F8+tube+straightener&qid=1659051025&sprefix=3%2F8+tube+s%2Caps%2C151&sr=8-5
https://www.amazon.com/S-U-R-BREZ400-Roll-Brake-Tubing/dp/B008BRHCG4/ref=sr_1_1?crid=19FDDXRDQU7RO&keywords=3%2F8+sur%26r&qid=1659051051&sprefix=3%2F8+sur%26r%2Caps%2C123&sr=8-1
Learn to use these tools and you wont need any rubber in a trans line. On a fuel line the only flexible line would jump from the frame to the engine.
