I realized this combo in a game against a bot, testing the new Guilds cards. It is pretty easy to play, get a Journeyman asap and therefore I recommend to open Silver/Silver, Journeyman/? or even better Journeyman/Tunnel on a Baker board. When you play the Journeyman, name Tunnel and discard them. You might want to buy another Journeyman soon after that, with 3$, buy Tunnel. When you have your Journeyman, you don't that many Silver, and you cannot draw Tunnel dead with your Journeyman. With Counterfeit on the board, get it over your first Journeyman. It will increase the power of this combo significantly as it allows both Copper trashing and a +buy, which can be used to get more Tunnel, or in the Endgame Province+X as you can easily counterfeit a Gold.
I was able to buy 6 Provinces, a Duchy, an Estate and of course 5 Tunnel with the help of Counterfeit and Candlestickmaker in 15 turns. I know the bot did not play well, and I might haven't played perfectly, but this seems to be a strong strategy.
Here is the log:
http://dom.retrobox.eu/?/20130726/log.505cc11ea2e6483e027bc556.1374866691284.txt