Inspired by Pete's ( Downwinds) article, below is my attempt at making my own dump load with encapsulated resistors.
I picked up a few stove heater elements from the local dump. These are flat on one side, I figured the flat side would transfer heat into a heatsink better than a round heater element. I cut two of the elements into short straight lengths, and ended up with 12 lengths in all. I mounted 10 of these ( one I broke and one I wanted to keep for testing ) onto a short length of aluminium rectangle section.
Each element draws 2.2 amps, and I've wired up 2 lots of 5 in parallel, controlled by 2 switches. Each switch can switch in 11 amps, so both switches on will draw 22 amps, or about 260 watts at 12 volts. The finished dump load has a 120mm fan to keep it cool, and fits inside a well ventilated case. At full load the case is warm to touch.