The couplers are not screw type so be careful while fitting and removing them. High side coupler will have some pressure under it and can kick back hard on removing.
For checking the pressures..
First take ambient temperature reading.. Note that and see the pressures on chart according to that. Purge the air in pipes with some gas. Hook up the gauges and start the car. Turn AC on full and let the system stabilize for about 2-3 minute's during all this process keep the front door's open or move that air circulation mode to fresh air.
Check the readings after about 2-3 minutes by increasing the RPM and see if they match with the readings on that chart. Hold the can upside down and charge the gas slowly don't open the valve fully just charge less and stop again check pressures and proceed till you get the desired pressures.
And if you have a pedistal fan at home then that would be even better if you will keep that infront of condenser. Don't pour water on condenser during this process although you can wash it before doing this.
