How had revolutionaries spread their ideas …

1)After 1815, many liberal nationalists went underground for the fear of repression.For example: Giuseppe Mazzini was an Italian revolutionary who founded two underground societies; first Young Italy in Marsellies and then Young Europe in Berne.Following in the footsteps of Mazzini, many secret societies were set up in Germany,France,Switzerland and Poland.
2)Romanticism was a cultural movement which sought to develop a particular form of nationalist sediment.The Romantics used folk songs,folk poetry and folk dances  to popularize the true spirit of the nation.For example:Karol Kurpinski celebrated the national struggle through his operas and music in Poland.He turned folk dances; like polonaise and mazurka into nationalist symbols.
3)Language also played an important role in developing nationalist sediments.For eg: It was mainly used as an instrument when Polish language was forced out of schools and the Russian language was imposed everywhere in Poland.