Use simple agar medium supplemented with 0.25% Glucose and 1% Cellulose or CMC, keep the pH at 7-7.5. Use the soil dilution (or any other source you are using for screening) of 10^4 onwards on these media plates as pour plate cultures. The clear zones arround CFU indicates the cellulose hydolysis qualitatively. Hope the procedure works for you.
use minimal medium contaning carboxy methyl cellulose (CMC) assole sourse of carbon.
After incubation fill the plate with congo red foklwed by NaCl. Colony having ability to hydrolys cellulose will zone clear zone against red background