Are there any special techniques for tempering dark chocolates with different cacao percentages?
You're first melting it all and mixing it together, right? You can just compute the cacao contents of the resulting mixture. For that you'll need to weigh the three batches. Say the 54% batch is 200g, the 63% batch is 150g and the 86% batch is 100g. Then you have a total of 54% * 200g + 63% * 150g + 86% * 100g = 108g + 94.5g + 86g = 288.5g of cacao out of a total mass of 200g + 150g + 100g = 450g. So the resulting cacao percentage is 288.5 / 450 = 64%. Now just treat the mixture as you would 64% cacao chocolate (since that's what it is).