Here's how I identify and document spray planes.
Equipment
Canon 20D with Canon 75-300MM lens--8 megapixel 2/3 full frame sensor, time 
  set to Zeit clock
  Sony DSC-W7, time set to Zeit clock
  Leupold 10x42 binoculars
  Flip Ultra HD video camera, time set to Zeit clock
  The Canon and Sony cameras timestamp their photos in the EXIF data and the 
  file, the FLIP video doesn't timestamp the file and I haven't opened the 
  video in a video editing program to see if it's timestamped anywhere else.
  Zeit radio controlled clock-accurate to 1 second
  Sony VAIO desktop computer, computer clock set to Zeit
Software
Canon EOS Viewer Utility to convert raw files to tif and jpg
  Adobe Photoshop CS
  Paint Shop Pro 5
  Flight Aware
  Flight Explorer Personal Edition
Technique
I can see planes flying out of LAX as they cross the Nevada/California 
  border by looking south west from my front door.  When a plane starts 
  chemtrailing I start shooting with the Sony camera to document the spraying. 
  When the plane gets closer I start shooting with the Canon and I can usually 
  get a very good shot of the plane as it overfly my house.  Once the plane is 
  over my house I go inside and sit down in front of my computer that has 
  Flight Explorer showing the planes in the Las Vegas airspace.  I use the 
  FLIP video to shoot my Zeit clock and then the computer screen as I right 
  click the airplane symbols to display their properties.
Hours later after I'm done shooting all the planes I use the EOS viewer 
  utility to process the raw images to tifs and use Photoshop to expand the 
  image to 100%.  The Sony images are shot in jpg and copied from the memory 
  stick to a folder on my computer.  Looking at the Canon images I can see the 
  planes paint scheme and can identify the type of plane.  For example, the 
  Virgin airplane that chemtrails in the morning is Virgin flight 404 or 
  VRD404.  It has a distinctive paint scheme of a white underbody with red 
  tail and red engines.  Flight 404 uses an Airbus A320 airplane. I identified 
  this plane by using the FLIP software to run the video of Flight Explorer. 
  I look for the Zeit clock time similar to the timestamp on the Canon and 
  Sony images.  Running the video shows all the planes in the Las Vegas air 
  space and sometimes it's easy to determine which plane matches the still 
  photos and other times it's very hard since I don't yet have a full plane 
  paint scheme database to refer to.  One of the planes that was very hard to 
  identify was the AirTran TRS890 flight with aqua underbody and blue engines 
  because AirTran isn't a major carrier.
There is one flaw in my technique that would make it hard to assert that the 
  plane I'm photographing is the one that is chemtrailing.  And that is I know 
  the Sony images and the Canon images are of the same plane but I couldn't 
  prove it simply based on the images I shot.  I have to have video evidence 
  of the chemtrailing plane that I can match up with the still photographs. 
  the next time I go out to shoot I'll use my flip video to video the process 
  and that should take care of that aspect.
One of the things we have to be concerned about as we document aspects of 
  the chemtrail spraying is that our evidence must be of the highest quality 
  and irrefutable.  Otherwise our conclusions can be questioned and our 
  credibility can be destroyed.  This is why I'm trying to have the highest 
  standards in my work and I hope others would follow my example.  For 
  example, I am very disturbed by the recent articles written by Dr Ilya 
  Sandra Perlingieri.  The science behind the collection of the air samples is 
  very weak and nowhere is the "maximum contaminant level" defined.  I emailed 
  Bridget Conroy asking how the "maximum contaminant level" was determined but 
  I haven't gotten any reply.  This is from the Arizona Sky Watch web site and 
  I don't think it would hold up very well to scientific scrutiny.
We also took air samples in Phoenix, on non-windy days, using a HEPA filter, 
  then vacuuming the particulates from that filter into another pristine HEPA 
  filter, which we then emptied into a sterile container. We were amazed at 
  the huge accumulations of the same chemtrail metals noted above. We feel it 
  is reasonable to designate the "Maximum Contaminant Level", or toxic limit, 
  of these materials in the air particulates to also be twice that for surface 
  water. Again, this is due to the absence of any realistic air particulate 
  standards that would account for the health effects of these materials in 
  the air we breathe every day.