You need real brush strokes with paint. No way around that, if you want a convincing effect. If you have a lot of text to do, you can get by with 3-5 different brush strokes scanned in and separated from the background, then composited and deformed with the puppet tool to match the lettering shapes. It looks like a font has been used to generate the outlines, you could use a mask channel on a group folder to do that, converting the text to a selection and then to a mask.
Kalleheikki Kannisto
Senior Graphic Designer