Hello Francisco, your figures are most excellent and perfectly painted. For the SdKfz 251 it may be an idea to touch up the rivets slightly with a dark color, or with what is called a "pin wash".
With whitewashed vehicles I usually also use a millimeter small extendable graphite pencil to line in all sharp corners and edges and to make the slits in the visors and headlights. Hope you like these suggestions, they can be done very fast and the pencil can be sharpened further with a knife.
The pic of the UN white ROCO 1/87 vehicles are to show what I mean, they were all treated this way.