After falling for the mistake of not sealing before grouting, I took advice from here to prevent that mistake again as it will not come out completely.

The tiles I use are Porcelain and glazed. Despite glazed they stain as I later found out.
I obtained a recommended sealant in Spain and just used it to prepare the floor.
It suggested one or two coats first.
Quite surprised that it appears to not have sunk in any, but dried off OK after one.
Close inspection it appears t have ;aid on the surface and when I rubbed a small area with a wet finger and it seemed to wipe away and no trace left?

This time the grout was applied and much care to remove access and it appears to be clean with no stain. I am unsure if the sealant worked or just the cleaning of access grout was the key.
My concern now is whether to seal again over the whole floor after grouting. I am of the opinion from what I can see it isn't doing what I expected.
I am returning to the UK soon and perhaps I could try a trusted sealant available there.
Any comments?

yes you will need to seal again after grouting

Porcelain doesnt pull it on like stone does. It takes a lot of buffing off

If they are glazed then no sealer is required, it must just have been the cleaning off process.