Training with a monk is 100% efficient and it's the best melee training that you can get. If you train with a monk the times given to you by my calculators will be accurate to within the second.

* You can not convince monks, you will need a mage to summon one for you.
* You need 2 monsters hitting the monk to take it's shielding spots. Wild Warriors and Poison Spiders work.
* After these 2 monsters are hitting the monk, start attacking it with a weak weapon.
* You need 2 monsters hitting you for your shielding, the weaker the better.

There ig a glitch in Tibia that makes some monsters a bad choice for taking the monk shielding spots. For instance, if you use 2 rotworms every now and then the sequence will change and you'll move onto a shielding spot. You won't be able to bleed the monk so your training will effectively stop. This is no big deal if you're playing close attention, but if you're watching a movie or tv it might take you half an hour before you realise you're no longer bleeding the monk. If you use monsters that do this, you will need to stop attacking the monk for a couple of seconds, then start attacking it again.

For the weapon choice, use a weapon strong enough to bleed the monk at least once every 3 hits but weak enough so it doesn't die. You will need to downgrade your weapon as you get higher skills.