Not sure if your cellulitis is related to your crusting lesion problem, but if so, then the yellow crusts could also be impetigo. (Which is usually caused by staph. aureus bacteria.) If so, you also need to make sure you have extra hygiene measures, such as keeping fingernails short and clean, wash hands, not scratching the face etc.
Soolantra should be applied in the area where the crusting lesions occur, even when there aren’t any lesions at the moment.
Maybe I did get a few crusting lesions on my scalp, when I had the problem, but can’t recall that there were any other users reporting lesions on the scalp. Maybe you could skip the scalp until Soolantra proves to be effective on your face? (Otherwise you’ll have to use a lot more of Soolantra when you do both the face+scalp.)
Also note that Soolantra may give a bad reaction when starting, so you may want to start slowly. For more info, see: Bad first reaction