How do I clean my kitchen porcelain tiles and grout?

I use a paste of white vinegar and baking soda and scrub with a stiff bristled brush. I've tried that grout paint, but its really worthless and doesn't last very long when it does work

Make a paste of baking soda and hydrogen peroxide and scrub.

Once you have it clean, you need to seal it. Test to see when it needs resealed by checking that water beads up.

If you can't get it clean and paint it, use an artist's brush and exterior paint (enamel works really well) then seal.

Use soft scrub with bleach, then seal when done

I'm the old fashioned floor cleaner type. When it comes to tile, I get down on the hands and knees. I just use plain hot water and keep the water in the bucket clean and the tiles will come out bright and shiny. I always go over the grout with a rinsed sponge when I am done with one area. Any dirty water will settle on the grout and be left there to get dark, so I go over it last, using a toothbrush if they are real dirty. They should be their original color when you are done. If you are real bacterial conscious, you can do one last rinse with vinegar, or just put the vinegar in your wash water.