I agree wholeheartedly! I like your approach on this thread. By not playing the macho, I know it all, card you and many of us are getting some good suggestions.Nonsence.. No stupid questions..
I would add a suggestion to SmokeyJones post. After you do all the drilling take a string and tie a nut on the end of it (not the kind you eat or might live next door), perhaps in the 3/8" or 1/2" size and dangle it down near the hole you have punched in the drywall near the floor or wherever you are going to feed the coax through the wall. Have someone else direct you until the string shows up in the hole, who then pulls the end of the string through the hole. Tie some nylon rope, about 1/4" diameter will do, and use the string to pull the rope down through the hole in the wall. Then take some electrical tape, compress the coax together as tightly as possible, and tape the coax together, along with your rope and gently guide and pull the coax to the hole in the wall. I find that running the cable down through the wall without using this method often results in having cable bend in ways that make it impossible to reach from the hole in the wall. I've also found that Romex or hard electrical conduit can make the cable pull very challenging.
If you can't get the nut and string positioned at your hole, then there is a possibility that "horizontal studs" were used to conform with fire break codes. These codes vary quite a bit between jurisdications. In this case you have no alternative but to cut some drywall above the horizonatal stud in order to drill a hole though it. After you do that go to a hardware store where there is some good, knowledgeable staff available and ask them how to repair the drywall. More often than not, this type of help is only available at local mom and pop hardware stores, not in the big box stores.
I've lived in/owned some places with open beam/tongue and groove construction in the ceiling. In that case poking a coat hanger up through the ceiling is not an option. Some very careful measuring is required and finding identifiable landmark or benchmarks in the attic that correspond with the measurements you made in the room is important. One more thing - the sharpened coat hanger method is a shot in the dark and there is some possibility that you could poke into something in the attic that you don't want to using a metal object. If you have to push hard to get through the ceiling you might penetrate some Romex electrical wiring and the result might not be all that beneficial!
I lied, one more thing. Buy a stud finder at the hardware store. The "knock on the wall method" is sometimes not effective. Having a stud finder around is helpful for hanging heavy pictures and for mounting shelf supporting hardware, such as that holding up your counter.