Its really thick and viscous. Which was handy.
The method was get a flat surface so that the front of all the tubes were level with one another. The rear of the tubes vary in length but thats hidden in the box I made to house them. Secondly, a second straight edge to line up the first row of 9 tubes. After that, keeping the rows straight was easy.
Once I cut the scrap OSB board to make the housing, I put it all together with glue and screws, spray painted black and wedged it into the paint station.
I'll be making more tubes to fit on my inclined sides to accommodate my dropper bottle paints.