When you play an army like Chaos Daemons or Tyranids you will find it a bit difficult to separate the units from each other.
Once in my Blood Angels days I charged into close combat with two tactical squads. This was before i had heard anything about squad markings.
It caused a big problem for me when ever I had to make a sweeping advance since I didn't know witch marine belonged to wich unit.
This wasn't a problem I had for a long time, since Space Marines are easy to separate. One small number on one shoulderpad showed wich unit he belonged to, while the mark on his knee showed wich company he belonged to.
With Chaos Daemons and Tyranids you don't have that kind of squad markings since they don't adorn their armor (or even wear armor).
The easiest way to create squad markings on Bloodletters is to paint them in different techniques, one squad can be washed several times with badab black, one squad can be drybrushed with Blood red.
Although this is the easiest way to separate your squads, I chose another way.
Since I'm going for a "Skulltaker's Cohort of Blood" Formation from the Apocalypse Realod book, I'm going to need 8 units of Bloodletters.
I find this way the best way to mark each unit since I want all my Bloodletters to have the same skin colour.
Now there are three things I use to mark the Bloodletters: The horns, the tounges and the swords.
Look at this picture:
They look very much the same, but if you look closely you notice that some Bloodletters are missing their tounges, while some have bloodstains on their swords.
When sperating the 8 units (I only have 4 so far), I start by dividing them in two major groups, The black horned and the bone coloured horned.
Theese are then divided in 4 separate units (wich can be merged if I play a standard battle).
First we have the standard ones.
The most boring bunch, they have no bloodstained swords and their tounges have been cut off.
Then we have the ones with tounges, and clean swords.
If I want to, i can merge theese two into a unit since the swords will be the easiest to spot.
Then we have the third and fourth unit, wich also can be merged. First out, no tounges but bloodstained swords.
And the last group and most decorated one, tounges and bloodstained swords.
Unit 5-8 will be painted in the same way, but their horns will be painted in a bone colour.
If I want to play a game and use two units with 20 Bloodletters in each unit I can easily spot wich figure belong to wich unit since the first one will have Black horns, and the other bone horns.
The Flesh Hound will be a litte more difficult to separate since they dont have horns or weapons. Hopefully I'll figure it out... Or stop getting hounds :)
I finished sculpting the left hand on Angron, and it didn't quite turn out as I had hopes, but it looks ok.