I have a down sleeping quilt and am always making sure that it stays dry. So I use a waterproof bag, plus a waterproof bag which I can compress down to a smaller size. I also have another trick up my sleeve. Because I have a Thermarest Neoair mattress, which does not self inflate, I use a low tech option from Thermarest which is just a large yellow bag, with a hole in the bottom which fits the mattress valve. I just roll it up four, sometimes five times, and my mattress is inflated. The yellow bag then becomes my third line of defence because it acts as another waterproof bag to keep my staff dry. I have a rucksack cover but only tend to use it when the rain is belting down.