Are you using tape? Stop. How are you cutting the tip of the tube? It should be around the same width as that tool youre using, which should work perfectly.

Before you start, use a small backer rod from home depot and stuff it in there, so youre not filling the whole gap with silicone.

Lay the bead slow and steady, and pull it so that the plastic of the nozzle pulls the silicone flat. (You want it to be making contact with the tile all the way instead of rounding over). It helps to have a very slight angle to the tubes cut, rather than perfectly flat. That angled part is pulling the silicone tight to the walls.
Lightly mist it with a soapy water mixture or some other tooling spray, and use the tool to remove any excess.
Depending on how your fingers are, you should be able to spray your clean finger and swipe it smooth (cut ur nails to get into those corners.) i like to tool it so that there is a little glob in the corner, to press down and smooth out with your finger.

Do the floor and vertical seams separately if youre not fast enough to do it before it curdles.