Hi - I used that grout sealer. So far so good. Very big tip! - you can get applicators that work really well to spread the sealer, make the job very easy. They kind of look like small squeezy sauce bottles with those screw lids so you can moderate the amount coming out, but they have little brushes on the end that you run along the grout. Worked really really well, very easy, I got mine at Beaumont tiles - I have found some which apparently Bunnings have, though I don't remember spending $14.00 on mine, maybe $6.00? Anyway.
https://www.bunnings.com.au/qep-grout-a ... r_p6653823
Before I found the applicators I could see myself handpainting the seal on with a tiny paintbrush lol. Thought it would take hours - only took about 2 hours to do the whole house floors (and we have a lot of tiles).
Hope this helps.