i did these simple lil mods with stuff we all have around the house and my kettle cooked for 11 hours on one chimney of charcoal with no refueling!!
i saw the mod on the virtual weber site
first get 2 bricks, firebricks if you have them i didnt so i just used 2 red bricks
place the bricks about a 1/4 of the way on one side of your kettle
line the charcoal grate on the other side with foil
open the vents up to where they are barely open
pour a chimney of unlit coals on the other side, light 10 briqs and place on top
put the lid on and cook all day!!
mine held a temp of 270-300 all day with no refueling, i think the temp was so high because i didnt place a water pan on the foiled side but ill try that next time