strep

My battery compartment is filled with battery acid/corrosion. It has a newer battery so it must be from the old one.
What is the best way to clean this out.
I already wiped it down. Also the negative ground is a bare braided copper wire. That is pretty corroded. I will replace that.
And one last thing....When my lights are on I get a fade that last a few seconds or more then comes back. It is quite subtle,But it is noticeable.Especially with the instrument panel lights. Could this be caused by the corroded ground. Any input would be highly appreciated.