How do I mass-link my INETNUM objects to my IRT object?

Normally you do not have to do this. It is sufficient to link the inetnum that is less specific to other inetnums (which would usually be an allocation inetnum) would be enough, because if the query uses a '-c' flag, the smallest specific inet(6)num object with an "mnt-irt:" attribute will be returned.

If you really need to do this, this can be done as follows: If your inetnum objects have a "mnt-by:" attribute, it is straightforward. Retrieve all your inetnum objects by querying for that "mnt-by:" attribute, modify them to include the irt object reference and add a "changed:" attribute line to every object.

Query for all your inetnum objects:

meijer@gebbetje:~$ whois -h whois.ripe.net -Tinetnum -i mnt-by SN-LIR-MNT -r > snlirmnt.txt
The RIPE Database reference manual, section 2.8. The '-r' flag prevents you coming up against these access-controls.

Update your inetnum objects using, for example, a variant on this script:
/^inetnum.*194.171.*/,/^$/{
/^mnt-by.*SN-LIR-MNT/{
         a\
mnt-irt:      irt-CERT-NL
}
/^source:.*RIPE/{
	 i\
changed:      Rogier.Spoor _at_ SURFnet _dot_ nl
}
p
}

# Call this script like this:
# sed -n -f  
# This script searches for inetnums in the range 194.171.0.0/16
# and adds a MNT-IRT and "changed" to them.

Send your updated inetnum objects to the RIPE Database using your usual method(s).

The update itself can be one large e-mail containing all the updated inetnum objects. This e-mail, assumes you are using PGP as your authentication method, can be signed as a whole, it is not necessary to sign all the individual inetnum entries. Although the message size limit is fairly generous, you should try to keep the overall size of the e-mail to less than three megabytes.