One of the only downsides to having server-side items is that you must be connected to the internet to use them. I did manage to create a huntsman training arena without being connected to the internet though. This will work with any item that uses different mechanics from stock (huntsman, mad milk, wrangler, etc.)
- Click the Create Server button (the little plus sign)
- Select the map itemtest.
- Once the map loads, join as a Blu Sniper. Press F7 once you've spawned.
- Click the Sniper check box, give him the huntsman, then click Apply Test Items
- Open the console and type
tf_bot_add 10 red
You are now equipped with the huntsman (with 25 arrows), you are invincible, and you have 10 bots strafing around trying to shoot at you. You can move to the hallway off to the side to camp and practice. I played around with this setup for a good 20 minutes and learned quite a bit with how the huntsman works.