Suggestions for ab exercise

I have lost almost 100 pounds and I have what I call a lower stomach and an upper stomach.  I have hanging fat from both and I am trying to find a way to help tighen up the muscle to help flatten the areas.  My husband says it is just loose skin but I think it is fat in the area.  I have a total gym I have been using, a gazelle, and a treadmill.  I have been doing the crunches on the total gym but does anyone have any suggestions as to how to help this area?  Suggestions are greatly appreciated.

I use a 7ft piece a pipe and hold it behind my neck and twist.  I have lost over 100 pounds and this helps me devleop abs.  You have loose skin more then fat.  You can tighten it up by doing crunches and by twisting with the stick.  A broom handle or a barbell can be used too.

I tried this before but it didn't feel like it was doing anything.  Are you suppose to feel it working?  Are you suppose to tighten the abs when you twist?

Hi, I go to a local gym that has machines set up like Curves for Women. It has a machine that is suppose to be working like crunches. It never felt like it really did much. It may have when using it in the beginning, it was more than I did previously which was nothing! But after months of doing these machines it was time to step it up a bit. Our gym had set up with this online program (your gym had to be affiliated, they numbered and matched all the machines) , but with this, I did sign up for the month free trial and have learned a lot of new machines in the rest of the gym and now do real crunches and have found a big change and difference in my body. I can feel them working, my waist has gotten much smaller, tighter and flatter overall. No, Im not ever going to lose all the skin etc without surgery, but my stomach area has done way better than I ever imagined. Now with these new things Im doing its really shaping up. I dont have to wear any type of panty girdle, or support of any kind. I started at 345 lbs and am now 208 lbs. I do alot of treadmill walking, squats and crunches and I love them. It is so good to be able to do this stuff I never imagined I could or would break a sweat just thinking about or seeing others do. LOL Try looking up online about doing regular crunches, side oblique crunches ( love these most!) and reverse crunches. I think you'll see a difference! Good luck! :)