Hopscreen is not only a great looking piece of kit it is also very effective and a great investment.
Like the false in the esky I've been using them for 5 years and they still look brand bew.
Whirlpool, as Rotten mentioned, is critical. More so than the hopscreen but i find in tandem they work like a dream.
Immediately after flameout i whirlpool and let it settle for 10-20 mins. After this time the trub has formed a nice cone in the centre of the kettle, away from the hopscreen. Drain through the chiller.
I sometimes use a hop bag if i am using large amount of hop pellets but not all that often. If you use a hop bag for the duration of the boil the amount of trub would be greatly reduced.
5 years, 120+ brews and never once blocked the chiller.