Hollowpointed,
gun cleaning rod with very long piece of cloth attached; smaller try Q tips; very very small try purchasing a can of "Bar Keepers Friend", sold at Jewel, Fair Play, major food chains. Put a bit of it in bottle, 1/4 fill with water, shake and shake, do again until it is clean.
Hope this will help you out.
have a good un..........
SHERMANVILLE ILLINOIS