screening as you put it, is a training tech used for keeping your canopy even.. growers use anything from chicken wire to string and make a trellis above the tops of the plants and than weave the branches into the trellis, allowing only the buds to go above the top of the screen... its a great method to control height, but can take a lot of work to keep up with it..
another method to keep height in check is lst, low stress training, in which you tie down the plant as it grows.. lst is an awesome tool for keeping plants in check, and i'm trying it out for the first time on my current grow as i'm growing a few sativa's and didn't want six foot monsters...
check out youtube and you'll be amazed at the amount of videos and info you can learn there...
can i use lst and later untie them and use scrog or is it one or the other??and do u recommend breakin/topping a plant at any time to encourage lower nodes to grow?