That guy's video is
WRONG and
DANGEROUS!
First of all, his string method will
ONLY align the front wheels properly on a solid rear axle vehicle with no bent suspension components and no bent axles. In order to use the string method to align an independent suspension vehicle, you have to set your string up exactly square based on a measurement to the centerline of the vehicle. At that point, you can set toe properly front and rear by measuring from the string to the wheel as he does.
Secondly, the suspension
must be loaded to measure toe. Suspension droop will significantly effect toe measurements, so if you do it up in the air, the toe will be
significantly wrong with a loaded suspension. Also, to properly adjust toe with the suspension loaded you must do one of two things. Either roll the car back and forth at least 10 feet after adjusting and before measuring, or use a set of turn plates under the wheels being adjusted. In order to center the steering wheel after toe has been set, you can turn one tie rod in and the other out an equal amount without disturbing your alignment settings.
I do all my own alignments at home and have done so for years. I use a set of toe plates to measure total toe, and roll the car to settle because turn plates are expensive. You can't measure toe individually with this method, but I just measure that based on fender lines since I expect the bodywork on my car to be close enough to true centerline. Total toe is what's important for tire wear and handling, thrust alignment isn't so necessary, so if it's off a degree or two, no issue. The only reason I do that is because it's a royal pain to set up the string square based on suspension centerline.
I measure camber with an angle gauge against the hub or wheel surface on a verified flat floor, also not a 100% digital measurement but perfectly OK since I can get each side to +-.25* of camber pretty easily. Caster is non-adjustable on a Subaru, but I measure that with an angle gauge on a flat part of the strut body (for MacPherson strut vehicles) and can also get really close side-to-side on cars that support that adjustment. The harder way to measure caster involves measuring camber as the wheel turns a specified number of degrees left and right and using some math, but my quick-and-dirty way has been acceptable so far. Caster is easy to tune by slight adjustments followed by road tests to make sure the car doesn't pull to one side or the other, since caster is the predominant setting that causes pulling.
Once I'm all done, I'll sometimes take a vehicle in to Les Schwab for a free alignment check to make sure I'm doing OK. I've never had a car out of spec.
I use a set of Longacre toe plates like these, and a standard angle gauge.