Should I index before or after importing a dump?
Yes, you can index them after you have imported (there will then only be the default _id index on the collection).  This is also recommended because the resulting indexes will be more compact and more efficient (for similar reasons foreground vs background indexing is preferred if you can afford to do it).  It will take some time to complete though, especially with 10 indexes to build.

To build after the import, simply do not define any indexes until after your import is complete, then use the ensureIndex() command to create the required indexes afterwards (with the usual caveat that such index creation will be resource intensive).  For more information: 

http://docs.mongodb.org/manual/core/index-creation/