tucking is always possible, comfort level may be a issue, and as always monitor the situation to make sure your not hurting yourself.
as for breast forms, there are so many types and materials its tough to give a generic call, I make mine at home out of a children's science project and zip lock bags it costs about 10$ and a half hour of my time. after a month they are holding up well. Worse case I need to buy some more school glue.
so I think more information will be needed before anyone can answer the question about cleaning them. but foam is usually pretty durable though regular exposure to water could result in them breaking down, and you dont want to submerge them or soak them but that depends on how they are sealed or coated.
Serena