I know there is a topic which tell you the same, but its to old to reply to it.
And its not explained.
1. Get your weapon of choice
2. Go to a target dummy
3. Activate 2 times Blood Boil to get you blood runes on cooldown
4. if both blood runes are on cooldown, you can spam any ability to get weapon skill ups, my favorite is peststrike, but you can also use death coil or whatever
The 2. blood boil will give you also a skill up.
I hope it doesnt only work for me
If something is not clear i can make a short video tomorrow