To use tumgreyspf, simply add this to your postfix configuration, and issue a
/etc/init.d/postfix reload:

/etc/postfix/main.cf:
---------------------
smtpd_recipient_restrictions =
	[...]
	reject_invalid_hostname
	reject_non_fqdn_sender
	reject_non_fqdn_recipient
	reject_unknown_sender_domain
	reject_unknown_recipient_domain
	reject_unverified_recipient
	[...]
	permit

smtpd_sender_restrictions =
	permit_mynetworks,
	permit_sasl_authenticated,
	[ ... ]
	check_policy_service unix:private/tumgreyspf
	[ ... ]
	permit

/etc/postfix/master.cf:
-----------------------

tumgreyspf unix  -      n       n       -       -       spawn
    user=tumgreyspf argv=/usr/bin/tumgreyspf