Seam sealer fail - help

Thanks for the tips. I am still trying my luck with the Dynatron 550. I have now put on 3 coats. This last one was slightly better because I decided to get rid of the gloves, and just use my fingers. It was real smooth, then as it dried it starts crackling and creating little issues, even pulling a little from the edge. Almost like it is shrinking/sagging. So now I dont really know what to do and this is the last step holding me hostage to get it painted. Now I am thinking maybe get some filler spray primer, and shoot several coats at it and see if it starts to fill the small crackles.