Heat a grill to medium. Remove the corn from the soaking water, shake it dry a few times and place on the grill. Grill, covered, until the kernels are tender, turning a few times, 20 to 30 minutes.
Meanwhile, combine the garlic, lemon juice and salt in a blender and blend until smooth (add a splash of water if necessary). With the motor running, slowly add the canola oil and the olive oil. Blend until the mixture is emulsified and thickened; then continue blending until a thick, buttery consistency is reached.
Remove the corn from the grill; pull back the husks, brush with the garlic whip, and sprinkle with feta and dill. Serve immediately.