I use coconut oil instead of butter and decarb in the oil. The same can be done with butter once all water is removed.
A good thermometer is handy. I use my infrared laser one after running a batch with a lab thermometer and seeing that it gave me the same readings. $20 at Canadian Tire on sale a couple years ago.
If you decarb pot in the oven on a cookie sheet or anything unsealed that stank coming off it are your terpenes and esters. Very low boiling point compounds that you lose. Decarbing in the oil keeps most of them in there. Has very little odour when I cook a batch right beside my chair in the mancave.
I do mine on a hotplate in a cooking pot with a piece of wire screen on the element. Once all the water is gone just raise the temp slowly toward 250F. Around 235 you should be able to see very fine bubbles on the surface. These are the CO2 molecules breaking off the THC/CBD molecules and floating to the surface. Depending on how fresh the pot is and how warm it got during the infusion process there may not be a lot of bubbles as much of the pot is already decarbed. Just watch the temp and try not to go too much over 250. Take it off the element for a bit in needed. Stir once in a while to loosen any bubbles and once you can't see any more bubbles you're done. I let it cool to around 212 then add about 5% by volume liquid sunflower lecithin to help with absorption when eaten.
Now you'll get the full effect of the THC and it can still be used for baking.
The link in my sig has a lot more detail.