Yes it depends. If you are flexible enough then fighters would use shin but the ball of foot works well in distance. http://www.kyokushin4life.com/forums/technique/2415-roundhouse.html
I have seen quite many shinkyokushin karate people talking at kyokushin4life.com forums. Maybe they can help you out? What I heard was that Shihan Midori is leading the organization right? I can't help much because i only find IKO1 kyokushin around where I live. Osu.
osu. have you tried methane liquid(?) or methonol? or whatever is called similar. I have used it to remove sticky sprayglue stuff that was on my artwork.