Top dressing (infill) is optional but sand is recommended at a minimum. Use crumb rubber or walnut shell (not visible) up to .75 lb with sand and Fresh Pet TD™ for dogs. One lb of large ballast with one lb of small ballast or Fresh Pet TD™ is recommended after the optional shell, cork or rubber is applied. Increase sand to 1.5 lbs of each type, if no crumb rubber, shells or cork is used. This can be adjusted depending on turf type and climate, etc. Pre-emergent before top dressing is optional for weed prevention.