Working on a 92 SC. Yesterday the A/C started alternating between blowing hot and cold. I thought it needed charged since I usually put a can in every summer. It has 134 in it. Today it started blowing hot and smoke coming out from under hood I shut the A/C off and it stopped. Does this point to a bad clutch or a compresser. If it is the clutch when I recharge it how do I add some oil to the compresser ?

the clutch doesn't use any oil, be safe take it to a EPA 609 certified tech.

also you shouldn't need to charge a system every year, my 94 still blows cold and never needed serviced. your system has a problem.