I am formerly an officer at my club in Katy, Texas, Space City RC. Ours is a private club for members only.

Our facility has signs posted and has a combo locked gate.

I think the best course of action is to welcome the tresspassers with an inviting and friendly tone.

Encourage them to join. Tell them what the membership benefits are.

Do this every time you see them.

If after a resonable number of attempts (like three) to get them to join fails, then have two or three members confront and politely ask them to leave.

If they refuse to leave, call the Sherrif's Department and inform the offender that you have called Johnny Law and they had better leave.

By the way, I have my Texas Concealed Weapons Permit and I am armed pretty much 24 / 7. The only way I am going to produce my weapon is if I intend to use it.
I will ONLY use it to protect my life or the life of an innocent bystander. While completey legal as an escalation of force under certian circumstances, absolutely nothing good can come from brandishing a firearm in an effort to get some one to comply. You do not produce your gun unless you intend to kill.