Yes, of course, having a multivisa to Spain, you can visit all the Schengen countries before the expiration of the visa.

Having a valid Schengen multivisa, you can freely enter Bulgaria and stay there until the end of the document. The main condition for using a visa is that you can not stay on the Schengen territory for more than 90 days for one trip. Citizens of the countries of the European Union, America, Israel, Australia and Canada can travel to Bulgaria without a visa.

To obtain a national Bulgarian visa, it is enough to provide the passport itself, a color photograph, plus copies of all the completed pages of the internal passport. Document processing takes a week.