im not absolut sure but i would suggest that you paint in LIN color space.
if you want only clone areas i guess it doesnt matter if you are in LIN or LOG space. but if you want to paint color to your image you must be in LIN color space. keep in mind that the color you added (painted) never was in LOG space. but this is the same like comp cg footage with LOG-LIN-LOG livefootage.