Using infinitives after prepositions

Spanish infinitives are often used following prepositions. Here's an example from the news: Unos 300 obreros despedidos amenazaron con cubrir de basura el centro de la capital paraguaya. (Some 300 laid-off workers threatened to cover the Paraguayan capital's downtown with garbage.) Although that sentence is an exception, the infinitive in such sentences is usually the rough equivalent of the "-ing" form of English verbs. Study the grammar lesson...