How to quickly select Necronomicon Archer to use mana burn

When I use necronomicon it summons two units, warrior and archer. How do I quickly switch to archer to use mana burn before my target gets out of range?
Using tab switch it can be slow (especially if I'm playing Chen or Beastmaster who have more summoned units) and clicking the archer is unreliable if everything is clustered.
How do professionals do it quickly?
Best Answer
You can set "Select All Other Units" to "2" for example and once you have popped the Necrobook you can just use q and cast it. (You might have to press TAB before if the Archer isn't the first unit)
If you are playing a hero that already has units (such as Nature's Prophet, Invoker or Beastmaster) you probably need to use Control Groups.
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UB Necronomicon | Mana Burn [Magic Arena]
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