UV dye will probably help for anywhere but the front compressor seal. Unfortunately, dye is hard to see there because of the clutch magnet and pulley.
After some time (a week or two) you might see some dye on the underside of the compressor-- get up under the car to see it.
Best bet is to charge it and check with a GOOD refrigerant detector (the kind most of us do not have). I tried a detector of the HF/Amazon variety and it was junk :-(