ferreting to longnet's can be fun, but again, horses for courses.
If you have a big banking with 300+ holes in, then the best bet is to longnet the top, bottom and sides of the bank, then you want additional nets running top to bottom every so often as in big sets the bunnies seem to hole hop. Eventually they will flee but depending on the size of warren and amount of ferrets used, it can be a while.
The best day i remember with the nets was on a hedgerow, longnets either side. I did two hedgrow's about 60 yards long each it was fun, especially because i was on my own, i must have bee