What exactly are you having issues with? I can't see anything in the tab that should be giving you problems with stretching...
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Quote by Master Foo
“A man who mistakes secrets for knowledge is like a man who, seeking light, hugs a candle so closely that he smothers it and burns his hand.”

To be honest, keep trying to play the song would be your best bet. It's just stretching so just stretch, I guess.
The more you stretch the better you get at it, but don't do over do it. Good things come in time
Learn Siege Engine by Buckethead. It is one of the songs that made me stretch my fingers like never before, I believe it will help you.
Quote by ChemicalFire
You get my first ever lolstack

The image in my head is just too funny for words at this point

Aw yeah.
Just be careful with stretching exercises, you can over do it and injure your arm. If you experience any pain at all, stop stretching straight away. Try some small stretches to start with, and dont over do it, then only work up if all is OK.