you need a budget to market. nothing is free. P.O.P. (Point of Purchase, i.e. flyers, posters, etc) cost money.
you don't promote people, you promote products. the song is the product. promote the song not the artist.
I never heard of a producer being marketed. very strange, waste of money. but it's common for a producer to promote a song they produced for an artist.
to market properly you need to know what you want from it, what are the goals.