just read properly through the water hash method that site mentions... nobody seems to give importance to freezing the weed before you do it. so go along with what the site says if that is your chosen method, but leave the weed in the freezer for the whole day before that, and instead of water prepare an ice bath (a bowl full of crushed ice and water - temp will be at 0 after about 20 min) and blend it together.
also, "window screen" will leave you with a harsh-tasting green pulp. buy 40 - 60 mesh wire screen to filter if you can, do a bit of research on the internet it can't be that expensive.
a friend of mine grows on a very large scale though and he detests water hash, so just bear in mind not everyone likes it...