I completely understand mate, no problem. It should automatically create a vmt file as well. Should go like this:
First of all, translation because my OS is in Portuguese (my language): Guardar = Save, Os Meus Documentos = My Documents, Abrir com... = Open with..., Escolher programa = Choose program
Open the image you want to make a spray of with VTFEdit.
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Press Ok.
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Go to the File tab and press Save.
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Type the name of the file you want where "yournamehere" is. then Press Save and that's it!
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The .vtf and .vmt files are surrounded by a black box. It was assembled in MS Paint in a hurry, sorry for that.
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If it is not working this way, then unfortunately I don't know what is the matter. You'll have to consult the author's website to figure out a solution. In the meantime, if you need that spray bad, attach the file that I'll convert it and then post back here.