I tooka old plastic mini blind adjuster rod put a red rubber tip on it & a decal in the middle of the rear window. Stick the rod in the crank handle & line up the decal with the stick, back up till it touches the window decal & I'm lined up.. Total cost $00.00 & I only have a 3' rod to carry along....
I got the pair of magnets with the telescoping rods and what John calls the 'Ping Pong Balls'. and the trailer and tow vehicle line up fairly easy...and yes, practice makes it easier. Good way to go, although the mirrors look really useful too!