I actually forst saw this video on the DVD extras for a Mary-Kate and Ashley film years ago where their hairstylist was talking about how he did their hair and it's really really easy to make. All you will need is:
I don't think the type of salt really matters, I've used Sainsburys Reduced Sodium Salt as it was all that was in my cupboards. Pour about 1 heaped teaspoon amount into a clear plastic bottle which you can get really cheaply in most stores in their travel section
Next, add about the same amount of hair gel. I've used VO5 Mega Hold Control Gel which i got as a freebie from when I worked at a magazine company that has been lying around in my room for so long, again I don't think it matters too much what gel you use.
Then, just fill the rest of the bottle with water, shake and voila! I've decorated my bottle with nail varnish but that's totally optional. You can experiment with different amounts of salt and gel to get the perfect mix for your hair but this is the ratio I use for mine.
All you have to do now is spray the lengths of your hair (I think it looks nicer when you use this on your natural hair, no straightening etc) with this, work it into the hair with your fingers and you're ready to go!
I have no idea how this compares to other surf sprays because it's been so long since I've bought one. I may get one and do a comparison review soon though.