1. How do you guys ground yourself before doing the thermal mod?
Special bracelet. Really cheap, can be bought everywhere. Also, do not wear stuff like whool. Simple trick can be to take off your shoes and let your bare feet touch rubber. Rubber mat or something.
2. Do i need to remove the battery of the mix plus? If yes, how to safely remove the battery?
Officially, yes. But if you are careful not to touch anything, it cannot do much hard. Actually, I have read more about people who messed up the battery than people who got statically loaded and blew up the chipset.
3. If i must remove the battery, do i need to do it after or before i ground myself?
As said above, just watch out not to short circuit anything and you will be fine.
4. How much is the dimension of your copper shim, i really need to know the thickness too, as some reccommends 0.5, 0.7 , 0.8 , and 1.0 mm.
Mine are 1mm thick and fit just fine.