Best way to do it is to spray the whole can in while at idle(if your
IAC works ok it should adjust and keep it running enough), don't rev it and switch it off when can is empty, you want the stuff to sit on the pistons and ports, hence no rev, let sit for 15 mins, then start and rev(may need to hold throttle open to get it to start)
If it doesn't smoke....there was no carbon/gunk that got loosened up.
If your running E85, water meth or race fuel, there will be no carbon.