ftp server on PF host with ftp-proxy

[mk]

Hello all

sorry for my silly question but I went through man pages and I'm still not 
able to configure my ftp-proxy properly.
I have OpenBSD which hosts standard ftp server and I want it to be 
accessible by passive connection from the internet.
This host has public ip address. Could you please post me just simple set of 
PF rules and flags I have to use for ftp-proxy?
I used ftpsesame for this purpose without problem so far, but I want to 
replace this software by ftp-proxy which is by default in OpenBSD.

Thank you very much for your time and help

MK