I mostly use the flat and the side of a cut-off or thick wheel. Regular drill. For corners, something like this
Grinding, Point, 3/16in - Rotary Tool Accessories - Finishing Tools - 3DY26 : Grainger Industrial Supply
The stones disintgrate and find their way under saftey glasses and in corners.
Don't know what that latest project is but I'll guess it will turn out sweet.