With a slide bar you can use a pre-made wrapped set. Get a clamp and 16" or so spring. Run the lines up to the spring,make a loop,put the clamp at the top of loop.
When you turn the loop will straighten out.
It is deceiving how long they need to be. Especially when you hook to a trailer has the glad hands in the corner instead of in the center like they all ought to be. Don't ask me how I know this.