Just be careful to not hydrolock the engine because you are sending Berryman's B12 directly into the ports that run to the intake valves --- it's a very short run.
If it's never been serviced, you may have to attack this more than a few times. But start the engine after a couple of cupsful of B12 so that you don't drop a big glug of the stuff into just 1 or 2 cylinders.
I think using a wire is a good idea - but the best wire I ever found for this type of cleaning is some old mechanical speedometer cable chucked up into a low RPM drill and GENTLY pushed into the port.
I've done that spinning speedo-cable thing many times successfully on plugged Honda EGR systems (our vehicles don't have an EGR system to which I have any knowledge) and it could always earn me lots of money whereas the dealer said they had to replace the manifold - for yards of end-to-end greenies.