Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Size
MDATA_BRUSH_FALLOFF_RADIUSParameter: Strength
MDATA_BRUSH_FALLOFF_STRENGTHParameter: Mode
MDATA_BRUSH_MODEParameter: Update Normals
MDATA_BRUSH_UPDATENORMALSParameter: Visible Only
MDATA_BRUSH_VISIBLEONLYParameter: Preserve Boundary
MDATA_BRUSH_PRESERVE_BOUNDARYParameter: Surface
MDATA_BRUSH_CONNECTEDParameter: Preview
MDATA_BRUSH_PREVIEWParameter: Space
MDATA_BRUSH_RESTRICTION_SPACEParameter: X
MDATA_BRUSH_RESTRICTION_XParameter: Y
MDATA_BRUSH_RESTRICTION_YParameter: Z
MDATA_BRUSH_RESTRICTION_ZParameter: Falloff
MDATA_BRUSH_FALLOFF_MODEParameter: Width
MDATA_BRUSH_FALLOFF_WIDTHParameter: Spline
MDATA_BRUSH_FALLOFF