I googled lymph nodes and wound up on wikipedia. It states:
Humans have approximately 500-600 lymph nodes distributed throughout the body, with clusters found in the underarms, groin, neck, chest, and abdomen.
If you are painting other parts but your thoracic duct seems especially fragile at the moment at receiving lugol's, then why not focus your painting on the farthest lymph nodes you can locate from the thoracic and work your way up? or work your way in if you have no problem painting above the thoracic.
so, groin, neck, underarms, abdomen and then chest?