Hi Iceman. What you were doing there was really grilling and using the coals to one side to provide areas of direct and indirect heat. If you are planning on smoking - say a pork shoulder, ribs or a brisket - you will need to change the way you use the coals in order to provide much lower temperature over a longer period.
When it comes to low and slow on the Weber Kettle you need to ignore what they tell you in the Weber manual. By using good quality briquettes in a minion or snake arrangement you can keep the cooking temperature at a steady 110-120 C (230 - 250 F) for 8 hours with minimum attention. Rather than light all of your coals before they go into the Weber you place them on the charcoal grate unlit and allow them to burn slowly whilst you control the heat by managing the air flow. The photos below will give you the idea.
Firstly use good quality briquettes - restaurant quality if you can get them. These may seem more expensive up front but they will burn much slower than standard grilling briquettes and you will have better temperature control with them for longer.
Arrange them at one side of the Weber and place any pellets or wood chunks that you want for flavouring on top. Light about 7 or 8 briquettes in your chimney and place them at one end of the snake. The burn from these will slowly progress through the unlit briquettes over time in a very controlled way.
Place some foil on the cooking grate directly above the briquettes to help spread the heat more evenly in the cooking chamber.
Once you have added the lit briquettes make sure that both the top and bottom vents are fully open and put on the lid
Monitor the internal temperature until it is up to 2/3 of the desired temperature. At this point close the top vents by 3/4 (leave 1/4 open - see last picture) and half close the bottom vent.
As the temperature approaches the desired smoking temperature gradually close the bottom vent further until the temperature stabilises. The bottom or top vents should never be closed completely or the burn will go out.
Remember to raise the temperature slowly. It is easy to raise the temperature but it is much harder to lower it once it has overshot your target.
In the 22.5" Weber (above) an initial 1.5 Kg of good quality briquettes can maintain a smoking temperature of 230-250 F for about 8 hours
In the smaller Weber you will not get quite a long a burn before you need to add more unlit briquettes but you should get 6+ hours.
I hope this helps