I guess we'd have to know more about your cooking - time, temp, brisket weight, flat or packer, etc.? CS electric smokers are very tight and don't generally need more moisture in a cook.
Most of the expert brisket cookers here (not me) say dry and tough = under cooked. Dry and crumbly = over cooked. You can search many discussions on this topic here. Try searching "brisket 101."