Green screen good. Blue screen bad. I've been a visual effects artist for 10 years and I have found that blue always more problematic than green in most cases. Now obviously if you have any green in the wardrobe or item your shooting you'll have to use blue. Also depending on what type of keying software you have blonde haired subjects in front of green can get, well hairy. I would not recommend any seems or folds in the chroma key material. Try to space you subjects as far from the screens as possible without breaking frame. Even lighting on the screen is crucial. If you have reactive lighting on the subject( fire/water/etc.) try to keep that from casting shadows or effect the lighting on your screen. Also, just because you can pull a good matte doesn't mean you will illiminate spill from the color of screen you use. Spill light is a color cast on your subject caused from the screen behind. Again as much seperation of screen and subject can eliminate alot of this.(posted 7579 days ago)Be careful with highly reflective props and wardrobe. Otherwise you will end up rotoscoping or garbage matting alot of frames. You can buy dulling spray from most production rental companies. They also have chroma key colored gaffers tape. A roll of this comes in handy for masking off stuff quickly.
Once you've wrapped up shooting and start pulling mattes on your pc,avid,inferno,photoshop you may encounter more problems due to format or just missed something in the eye piece while shooting. Don't panic. Sometimes it isn't one good matte for the job. You may have to take several passes at the shot and key specific areas at one time. Than you can combine all of the mattes to make a perfect chroma key. Alot of software has the ability to color correct certain colors to help remove a green or blue cast.
No chroma key shoot is the same. Sometimes you have no trouble and than there are the times where your pulling your hair out.
In response to making a portable chroma key screen it is necessary to know how large of an area you need to shoot. If you use fabric make sure it is secure at all corners especially if shooting outdoors. To manufacture a light weight large screen it might be best to look at rental costs before purchasing materials to build. Alot of equipment rental shops have green and blue screens of all sorts of sizes.
Hope this helped. Good luck.