Need Sanding Tips

I just finished my first board and it came out 90% good, except for my sanding. After sanding the hot coat,  I have about 12-15 minor sanding scallops about 1 1/2" long, elliptical, about 1/16" wide.  It appears to be in the hot coat and not penetrating the glass.  I hoped that these blemishes would fill and dissapear in the gloss coat , but you can see a slight low spot after glossing.  I’m hoping to one day have a flawless sand job.  Any tips to help my sanding are appreciated.  I am using a red Milwaukee variable speed sander and have it set between 2000 and 3500 (2 and 3.5),  the 2 sanding pads I use are a disk-it firm and medium,  100 grit then 220.  I feel that I’m keeping it flat and level.  Any suggestions on what I should or shouldn’t be doing?