I know that there's some compound you could buy to do this, but how about doing it for free? I tried and it works!
First of all, let me describe the problem and why we should fix it. Autostar (or Nexstar) controller will become not as responsive after some years of usage. When you press a key, you have to press it hard, or really hard, in order to have response. That happens mostly for the four directional buttons, and any buttons which you always press like the ENTER, and the MODE buttons.
I will not repeat how you to disassemble the autostar, you can do a simple google search and you will find it. In short, you need to remove four screws, and then you have to remove a clip which holds the flat cable to the LCD and that's it.
Okay, we have the keypad now. Notice that we're trying to fix the black dots (or circuits) behind the rubber buttons. Here you can see another keypad from another remote control which comes from a dead DVD player.
Gues what... Yes, I'm trying to cut the black dots from the useless remote control and to stick it on the Autostar! Of course, I did it for one button first as an experiment:
And then I tried the Autostar by assembling it and power it up, it works! And it's just very responsive now! Therefore, I proceeded to work on all the buttons which I frequently used. It takes around half an hour to do all these.
Now my Autostar is working as great, or even better than when I first received it. And a final word of warning: don't fix it unless you absolutely have to and it will definitely void your warranty if there is any. Good luck!