Lefty-loosey, righty-tighty
No, you need to lower both. Lower the bottom one first, then the top one down to it. Then hold the top on and tighten the bottom one UP against it so neither can move.
I use a screwdriver and a hammer
If you lower too much, the spring will come off it's top perch. Not a big issue until you unload going over a jump or something. Helper springs are used usually tho.