You may receive a blessing simply
You do not have to kiss the priest’s hand before you understand the custom. If someone asks Abouna for a blessing, many people kiss his hand because that hand blesses and serves the mysteries. You may also greet him respectfully and ask for a blessing simply.
What the gesture means
The honor is directed toward the priesthood and blessing, not toward the priest as a private celebrity. The gesture expresses reverence for the ministry Christ gives to His Church.
Now beyond all contradiction the lesser is blessed by the better.
If it feels unfamiliar
Ask what the custom means. A careful question is better than forced imitation. Many visitors first learn the meaning, then decide how to participate with understanding.
The important distinction is between reverence and pressure. Reverence honors the priesthood and the blessing given through it. Pressure turns a meaningful custom into anxiety. Coptic practice is healthiest when the meaning is taught clearly and received freely.
You may ask for a blessing, bow, greet Abouna respectfully, or learn the custom over time.
If you do kiss his hand, do it as a request for blessing and as honor for the priestly ministry, not as flattery toward the man. The custom should lead to humility, not social pressure.