You do need to wait for the grout to cure. I would think that three weeks is ample.
I would make sure that during that period that I keep my grout as clean as can be and especially free from any chemicals.
This sealant comes in many forms of application. I like the one with the sponge top applicator that you brush on like that old liquid shoe polish.
Read the instructions carefully and do the test periodically to see if you are getting the beading up of water as needed.
I have seen that some areas take three seperate applications each after prescribed drying times.
I have not seen any yellowing or discoloration at all.
I would suggest it. Keep it off the ceramic tile if possible, no problem if it gets on it, but just wipe it off.
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