Please help with SPF setup Postfix
 

In setting up a (hopefully secure) small mail server, I follow the tutorials and examples. The configuration file examples are rarely the same, sometimes achieving the same end in different ways.
Sender Policy Framework.
Reasonably straightforward to do by setting the public record TXT line at the domain DNS server. It tests OK, getting a PASS when sending a E-mail to a Gmail account.

Working it the other way, to check the mail servers of all the incoming mail, to reject E-mails that come from servers that fail the SPF checks, requires to meddle with Postfix.
It uses the "postfix-policyd-spf-python" program.

In particular..
/etc/postfix/master.cf
To enable the policy service is where I find two different versions I don't yet understand.
Code:
# Version1
policy-spf unix - n n - spawn
user=nobody argv=/usr/bin/policyd-spf

# Version2
policy-spf unix - n n - spawn
user=policyd-spf argv=/usr/bin/policyd-spf
Both "nobody" and "policyd-spf" are users in the system.
(found by cut -d: -f1 /etc/passwd)

The other file "/etc/postfix/main.cf does have an entry..
Code:
check_policy_service unix:private/policy-spf'
.. to be added to the smtpd_recipient_restrictions

So which is it to be?
Is it "nobody"?
If it is to be user "policy-spf", does one have to add a file somewhere else?

If you have set up Postfix and SPF, and know what to do, my thanks if you can help.