Install your shower tiles and apply grout. Once the tiles have been grouted to your satisfaction, allow the grout to dry for at least two days before you apply the sealant. Do not use the shower during this time.
Apply latex sealant to the tiles and the grout around them, using your sponge paintbrush and making sure that all of the grout is covered. If you are using an alternate sealant type from a tube, use the increased nozzle control that this offers to only apply sealant to the grout, if the tiles are ceramic and have been glazed. Pay special attention to corners or other edges where the sealant might not penetrate as easily.
Allow the sealant to dry for at least two to five days before using the shower. This will ensure that the sealant has plenty of time to dry.
Reapply sealant every two years, allowing the shower to dry for five days beforehand to ensure that there is no moisture trapped behind the tiles. This will assure you of consistent protection from mold and mildew.