Niko
Your right the use of the fishing string as a foundation can pose a few issues. I solved(attempted to) the issue two ways 1st boiling strands of string and some manipulation. This still didn't solve the issue for strands longer than 3 inches, so I heated stands over a candle while stretching taut.
One benefit of working with the medium of hot glue, its like working with Velcro.....peal off and reattach
The next step would be adding snow, my method is microballoons and white glue.