Caliper grease can work as well, if you don't have the proper silicone stuff. Not sure how well it will hold up over time though, by comparison.

If the aftermarket pads didn't come w/ their own shims, I'd assume that backing is meant to be used instead of shims - that may work well for all I know, but if that's the case, and you have all of the oem shims, I'd recommend just applying grease to those.

True about some pads making more noise than oem or equivalent, I've got Nissin pads on my civic and despite having less than 1/2 of the shims it's supposed to have (and 1/2 of those being aftermarket shims) they very rarely make any noise.