I have a few comments on that video. first of all if you want to do it yourself just wait for an 80+ degree day. The rule of thumb with high side pressures that will get you in the ball park is 2.5 times ambient temperature at 1500 rpms ( so yes you need to give it a little throttle). so its 80 degrees out. 2.5 x 80 = 200. your high side pressure should sit somewhere around 200 psi. However what many people overlook is make sure the radiator fans are working properly! if the heat is not drawn from the condenser the high side pressure will skyrocket even though it technically has a low charge. On some rear wheel drive vehicles with clutched fans the clutch may start failing enough to affect the ac performance.
Low pressure especially the ones like on the GP's compressor is variable and the low pressure gauge only wont tell you squat. It will only tell you when you have enough refrigerant to satisfy the low side but you need to add more to get the high side at the right pressure.
If you fill with liquid ( turning can upside down during fill) make sure to never let the low side pressure go above 50 psi because if liquid gets into the compressor it will instantly kill it. On the gp I believe the low ports are far from the compressors so there isn't much of a worry but I have worked on cars the low side is right at the compressor.
im not sure where this guy gets the info of using low fan speed. I was taught to use the highest setting without recirc and the windows open. Maybe he was using low fan speed because the ambient temp was down.
