Water base products can appear white when first applied but that is normal and the white will dry clear. Water base products have a temperature window and need to be applied in a non freezing environment.
Solvent base cure & sealers need to be sprayed in an open and unoccupied areas.The fumes from solvent base products can and will be very noticeable and irritating to the eyes and lungs.
To Spray or To Roll
Spraying a cure & Sealer is the fastest way but take notice of the wind and your surroundings. Cheap garden sprayers may or may not be able to handle these products because of the solid content. Be sure to use a quality sprayer. If you are using a high solid cure and sealer you may want to apply it with a paint roller. Wind can also affect your coverage. Rolling it on takes more time to apply. Chapin sprayers make a sprayer for these products model #1949.