I use pacific abrasives white rubber wheels, super cheap and work great on porcelain at the margins, Keystone diamond flexis for zirconia.
I would start bumping the temp up 5' at a time to try and get a little more shine on the glaze, might not need it. The pits could be from many things, its almost impossible to tell without eliminating one thing at a time. Could be gas coming through the porcelain, but doesnt look like it. My guess is either drying too fast when wet in oven, too much glaze liquid to glaze ratio, temp not high enough, glaze applied too thin, porcelain not sandblasted before glaze, or more than likely, the micro pits were in the porcelain and not necessarily in the glaze layer. Could be from uncondensed porcelain, vacuum, oven, heat rise too fast. Welcome to dental technology aka troubleshooting. Take notes, be scientific about it. Pits suck, they are plaque traps and are hard to manage until you find out what causes them.