rear tire pressures are low.. figure 10-16 psi..
if it's loaded and leaks you will need to break down and clean when fixing.
a jack and a small piece of wood can be used to hold a pipe wrench engaged to the plug while you turn the wrench with a pipe.
for the heck of it hit it with spray oil.. but don't count on it helping. most plugs are stuck because the PO was too cheap to cut a new gasket out of a cardboard box and instead glued it in with some goop that hardened.. or he tourques it to ni gajillion pounts trying to get it to stop leaking with the old gasket remnants still on it.
if the pipe wrench fails and you have a welder.. weld on a big hex nut.. just hit 2 sides oposed.. then yse a real wrench or socket / breaker bar on it.
weld heat helps it pop loose too.
other options are using a cold chissle and getting just into the flange of the plug but staying out of the pan metal.. then tapping it around once you get it to bite.
can also refile or grind new flats int he plug if it is rounded.
I useually don't dink with those. if a standard wrench don't do it and the pip wrench looks like it won't. I don't hesitate to weld a nut on it.
takes only a minute to drag the leads out and turn on the juice.
i'm not a fan of sandblasting.
it gets everywhere, and can deform small metal parts.
hand sand or buff with a 3m black pad.. do whatever body work you feel you need, then celan up and prime and paint.
break down tires from front rims and if really rusty, electrolysys dip them using a battery charger and sodium carbonate.. 12v 2+ amp charger.. negative to rim, positive to sacrifical metal.. don't let them touch..
once de rusted, weld up anything that needs welding.. can weld and redrill valve stem hole or weld a washer over it.. grind smooth.. then prime and paint. i reccomend an epoxy primer and paint fo rthe rims.. even if from a rattle can. it's tough and resists corrosive ballast materials.