Steering box lubrication

My 1970 Beetle steering box has grease in it. My question is can I just top up the grease in the box, and if so whats the best grease to add?

Must confess I’ve never used anything in the past. Good thread on this on VZi
http://www.volkszone.com/VZi/showthread.php?t=1217442&highlight=Semi+liquid+grease

Cheers Keith.
Interesting article but I’m still not sure whether to top up the grease and with what kind.
Or I could just leave well alone …

Alan