Where a failure case covered by a single flight manual procedure has handling difficulties or special procedures, these will be noted in the relevant procedure (such as advice to minimize brake pumping in the event of multiple hyd failures, if your brake system is running on accumulator power only).
A double or multiple failure which is not the subject of a specific AFM abnormal or emergency procedure may have handling or other problems due to the combined effects; these may not be identified, since there won't be a "engine fire plus depressurisation" procedure to follow, and the problem may ONLY exist in the combined case. In that case it is indeed on the shoulders of the crew's basic airmanship skills.
The idea is that such 'perfect storm' days are so rare that they should not be provided for, as there are such a huge number of combinations, each of which is very unlikely indeed.
PS obviously, those remarks apply specifically to our manuals, but I don't believe we're significantly different from other OEMs.
Edit: to clarify - usually double hyd failure is a sufficiently probable event that a specific procedure exists, which would include some or all of the advice suggested, dependent upon model.