judge
some of the kits have a small can of about 6 ozs of freon with a locking style filler valve right on the can for a quick add-in.
They do work, but you don't want to over-charge. Make sure something else isn't causing the lackluster ac first.
Check the fan clutch, make sure it is hooking up when hot and do a quick check for air leaks under the dash.
Look at the hose ends in the system, if you see oily residue around the connectors, that is oil from the freon and a little can be just fine and not be a big leak. Some of the recharge kits have freon with seal conditioner which is good.
There is a can of ac tune up from BG products that is an excellent product.
you might look for a BG dealer and ask for a quote to install a can of that.
It has a conditoner for seals, some freon, and special lubricants for older worn compressors to help them last, and other additives that they guarantee to lower the AC temps
PM me if interested and I can tell you more.