welcome to healthcaremagic forum
thank you for your query
propynate nf contain steroid
one so not to advise to apply for more than 4 wk .
you can apply xerina cream over neck and arm
it will take 7-8 wks to have response .
use good moisturizer cream for dry skin
penis skin is darker than other part but for dry skin you can apply that same moisturizer
if lesion persist better to consult dermatologist
i hope i answered your question