The sprays i've tried are Sealguard and LTP Grout and Tile protector. Both very effective and easy to do. But they get you high-as-hell if you don't ventilate the room properly. Enjoy 😉
Any of the above as paul or any water based specific "grout protector "will do the job if you don't want the high chemical smell , if you use the spays , please do ware a cartridge mask ( spayers chemical vapour) in a small space as these are not pleasent to inhale,