help with bodywork?

i grinded the welds down yesterday on my tail light filler, and it really didnt take much filler to get pretty even.. i used Evercoat Everglass, i spread it evenly around where i welded and sanded it down smooth with 80 grit on a DA, and did maybe 1 more thin coat of it around that same area and it was really even already, except one corner where i used a little bit more.. and now i primered it after sanding with 320 on the DA so it wouldnt rust overnight and i see 2 low spots that are barely noticeable, and a small spot the grinder must have hit.. i know im supposed to use regular body filler or maybe glazing putty over the evercoat, since its easier to work with.. but since i can get this Evercoat pretty damn smooth with the DA couldnt i just use a little more of it to fill the low spots and the grind mark? someone give me some tips.. i also learned not to tape off the area like i did and get "hard lines" but next time to fold the tape back so it doesnt form a line, it catches overspray and stops the primer smoothly.. thanks