OK.. first up.

Aux 4 and 5 are in fact 1024 resolution, they're just sampled at 1/2 the rate of the other channels. This is why we don't recommend you use them for primary flight controls such as aileron, elevator, or rudder.

Now.. you can move the aux 4 or 5 to the slider no problem using Origin mixing. Origin mixing says to take the physical value from the trasmitter control and apply it to only to the mixed channel while ignoring the channel it's originally intended to drive.

1. Disable the right slider in Code 17 (aux 3). This tells the radio not to use the right slider for Aux 3.
2. Create a mix with Aux3 as master and your brake channel as slave
3. Press page twice and select Origin mixing. This now tells the radio to use the right slider, but only for the mixed function, and not the original function.
4. Press page again and setup the mixing values as needed for what your brake actuation.

This logically disconnects the slider from the Aux 3 channel in the transmitter allowing you to make it operate the brakes.

Now you need to setup your smoke.
1. Create another mix, this time Aux 3 to Aux 3.
2. Press page once and assign this mix to the snap button.
3. Press page twice to get back to the original screen and adjust the values to make the smoke turn on and off as you want.

That should do it. I know it's a bit confusing.. but once the light goes on you'll find origin mixing to be incredibly powerful and useful.