Solid Hardwood, Engineered and Laminate Flooring - laminate question

Hi, I installed dupont real touch elite over flat, level, vinyl in a bathroom a year ago that went without a hitch. I'm getting ready to install the same floor in a bedroom, have pulled up the carpet and pad, all the staples, sanded the seams that were slightly raised of the 3/4 inch plywood subfloor, but am still left with a few dips in the center of the room. Can you tell me the best way to fill these -- roofers felt, or leveling compound, and if so which kind. This laminate is the kind with the foam underlayment already attached to the back of each plank.
thank you for any advice you can offer, I really love your forum -- you've saved my butt more than once.

Modified thinset tile setting mortar works pretty darn good for under floating floors, as long as it is not deep. The latex in the modified thinset makes it stick to almost anything, and it also makes it somewhat flexable so it doesn't crack up and turn to gravel or sand under your floor. Although, the first laminate class I went to many many years ago, when it first hit the market here in the US, the guy used sand to fill the low spots. Yes, sand!!! Hey, it workedand was kind of self flattening as long as you didn't get too much in the low spot!

I didn't think sand was too professional, so I only did it once, and felt uncomfortable when the homeowner was grilling me about it. :) But, it works. The sand has to be dry.

Thank you for your quick response. I will definately try the thin set. My father-in-law told me sand was used underneath the laminate in his kitchen. It looks and feels great. What kind of sand, though? Play sand -- the kind used for a kid's sandbox?

Any feedback....

I am thinking about installing a floating floor (dupont real touch elite), however, was concern about dishwater/sink leaking as I am starting with a level clean room (12x12). I may also do the dinningroom next to it if I like how this one works. Also, I have two small (20-25lb) dogs, will the floor get scrached by their nails?

Regards,

David