Using an air tank compressor with a regulator would be fine. A compressor/regulator directly into the fork could be bad. A regulator alone might not be able to respond fast enough to prevent the fork from over-pressuring, hence the need for an air tank volume. If the compressor is feeding an air tank, the air tank acts as a volume reservoir, in which case you could easily use it to pressurize the fork.

Back on topic, how did the fork respond after setting the pressure.