Hello, the earthing stake should be at the energiser and watered when the ground is dry. The separate enclosures can be connected with whatever insulated wire or flex you have. The bigger the connecting wire diameter is the less the resistance there will be. Electricity is like water flowing through a hose the smaller the hose the less flow. As to weather to run separate connections. Its up to you, whatever way uses the least amount of cable runs is best either direct from the energiser or enclosure to enclosure. Then wait until it rains and listen out for short circiuts.