I've also been using it for almost a decade. I usually have to: + find the largest source version of the font in question. common logos are frequently available

I've also been using it for almost a decade. I usually have to: + find the largest source version of the font in question. common logos are frequently available in vector format (I'm assuming you're using the service because the font itself has been outlined; you'd have no use for it if the font is either embedded or referenced). if bitmap, use google image search to find the largest size. + create a high contrast version. if vector, simply open in a vector editing app and make the text black if it isn't already, and remove any background. if bitmap, open in bitmap editor and manipulate image via channel editing or using levels, curves, or other method. + edit in vector or bitmap app to remove any overlaps. + save to highest quality JPEG and upload to what the font. + use what the font's drag functionality to combine letterforms that it (ridiculously) doesn't automatically detect such as "i". + hope for the best.