True, but the 90 days to activate doesn't override the, say, 14 days allowed in Hong Kong.
My company (which is very small) had not organised a dependent visa before so I had to figure this bit out too.
I downloaded the forms from the website (see above posts) and the details of which sections to fill is stated at the top of the first form.
Your husband needs to fill in any parts that ask for the sponsor.
I sent these forms in with my own and the company posted them all off together. It took around 4 weeks. We flew into HK and picked up our visas when we landed then popped over to Macau for the day to activate them.
I think it's worth asking your husband's HR dept to help you out here....most companies do.
PS: I took me ages to figure out the Immigration website, you're not missing anything, it's not all that clear at times!