You could use scraping, but it will be difficult to release all individual cells from the surface and from each other. Alternatively you could use sanitation, or a viability assay (XTT, MTT, WST etc) to determine residual metabolic activity.

biofilm producing organisms could be made adhered on the desired surfaces. from the surface the organisms could be detached by ultra sonication or water sonication process. the sonicated samples could be serially diluted and plated on selective or non-selective plate count agar media. following incubation 24 to 48 hrs at 37 deg cent the number of colonies obtained can be calculated as cfu/ml. Just you need a sonicator.