How strong to mix it depends on what application it's being used for, e.g. regular cleaning versus cleaning the enclosure of a snake with an RI versus disinfecting a used enclosure you purchased secondhand and plan to use for your animals. There's a good explanation of how to mix the product for each purpose on the Reptile Basics web site.
Once dry it's safe, so you can lightly mist the enclosure and wait for it to dry, or you can spray it on, wipe most off, and wait for the residue to dry.