I encountered something similar.
I would wash the end pieces with a mild soap and water solution cleaning with a small toothbrush. Blow out the end pieces and dry with a hair dryer and then let sit over night to fully dry. I dropped in a bit of powdered graphite from each side and blew out the excess. I then pressed the expandable pieces in and out to work the powder in. That cleaned and lubricated the inside enough the allow the end links to fully expand with no issues.
I would avoid any type of liquid lubricant because you are correct it would attract dirt and skin inviting the end pieces to become clogged again.
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