Jim,
I went to the same school that you did but you were a few years above me. That string you used is probably Barber string, its known as barber twine (as in the jackets) its what the fitters use to hand sew seams in the body carpets.
Dr Carpet
The long bulldog clips simply fall over and give you a straight line to work to, any one else just get some off cuts from the local carpet shop skip, burn a hole in a small area, take some tufts from the out side and sew them in.
Practise makes perfect.
Murky