You will not have satisfactory results repainting a
scrim. Scrims are not painted with paint, they're painted with dyes. Unless very diluted, paint tends to clog the holes, turning your expensive scrim into a solid
muslin painted drop. We used to use carcinogenic aniline dyes, not sure what the current practice is.
One possible solution is to use a plain white scrim and multiple
Rosco ImagePros in SourceFours to project the picture, then dissolve through to the upstage scene and fly out the scrim. Much more expedient/cost-effective to manipulate the picture in Adobe Photoshop and print it onto transparencies, and rent the accessories and if
nec. the fixtures, than to paint with dyes a 20' x 40' scrim which will always contain that picture.