I also use a Weber Kettle and I have more of a problem keeping the temps low versus high. I would x2 the comments made above
- do not use starter fluid. Go with a charcoal chimney starter and you will never look back
- pick up the charcoal trays mentioned above or create a similar set up using foil.
- Take a look at how the intake vent works on your kettle while looking from the top of the grill. There is really only 1/4" of range from the closed setting to the open setting and the more you are familiar with this setting, the more control you will have.
- Get a good BBQ thermometer and set it on the grate away from any water tray and away from the cold meat "air bubble".
- Definitely start out with more than 4 hot coals. I use the charcoal trays and I get the coals "1/2 way started" and then dump it into each of the 2 trays.