Definitely a two person job. At least one of the people just needs to hold the ratchet or the screwdriver, so it doesn't need to be a skilled person. I made my kid crawl under the truck, since I am too old and entitled to do so anymore.
Also, use a larger size Phillips head screwdriver on top, or the screw heads can deform. Size matters in this case. Also, recheck them later, as I had one that loosened up about a week later because my truck has a rubberized undercoating and the nut kind of sunk into it eventually.
(Technically, I guess all screwdrivers are Philip's screwdrivers, if they are owned by Philip.)