I've got a hound mix but don't intend to do anything with her. However, I did and will be in the future looking into some other hounds, like a blue tick.
From my understanding, you've done the right thing here so far. You have to slowly progress the dog into searching out the smell. Now, you need to get the dog to want to tree it.
This would be done with LOADS upon LOADS of praise and "Good dog!" over and over.
The dog can snuff out the scent. Great, it knows exactly what it smells like and it wants to hunt it down.
You might want to try getting a coon hide and starting low on the tree and move it up for the dog to reach and grab. Continue to praise, praise, praise constantly when it does it right.
As it gets the object (hide, rag, etc.), begin to move it up the tree until it can't reach it but simply "trees" the object and barks, etc., as you want. This could be done with a rope and lifting the object up if needed, but it may not be needed. You kind of get the general drift as to little games to play to get the dog locked into getting after it. Those who hunt will probably, ultimately, tell you to catch a coon with a trap and then hold the dog, let the coon out, and let it tree once you've progressed well with the inanimate objects.
One good key to remember is to have some treats or something on hand and when the dog trees the object and such, decide on ONE phrase (e.g. "It's dead. Good boy.") to use ALL the time to let the dog know it is done and to stop. You might get the dog's attention, say the phrase, give it a treat and then walk away with the dog. Leave the area. This is important to be able to get your dog to differentiate between game on and game over.
Maybe that is a start in helping. It probably isn't the most help, but just some commentary I've gathered from some coon hunters in the past.