I just rebuilt 2 7-speed Suntour freewheels and even when cleaned and serviced they don't seem as quite as Shimano.

I break the freewheel nut free while on the rim then take my a part over a magnetic mechanics tray. I put a rag under the freewheel to hold the inner race up (bearings in place) and remove the outer race and bearings and put the bearings in a small container to soak. The remove the inner race and those bearings to soak. clean the parts/races. To hold bearings in place and provide some lubricant I use a light synthetic grease. Add oil as needed afterwards