How do you use proguard just to replace class names and variables?

Question

I had a horrible time with proguard and ultimately decided not to use it to remove code. Instead I intent to use it just to replace the variable and classes name just so that my code is not all available with a simple JDAX decompile. Anyone knows how to use proguard (or R8) to just simply "obfuscate" the code (i.e. minify the variable/class names) without removing code? Also is there anything better than proguard (R8) for obfuscating purposes?