Ragnarok.Calif said:
The pyrosoul recipe is 60 fire, 15 ice, 30 earth, 15 water.
Just quoting this 'cause it seems to be the only one of them that is listed on wiki, so this is all I can advise on really.
There are two main challenges with synergy. The first is what I'll call Weakness Reduction (WR), in that when you feed one element, the element that it is strong against will go down by 2. The challenge with WR, is that in the above example, say you start with fire, and cap it at 60, then when you go to feed your water, you'll lower your fire by 2 points each time. So generally speaking, the best way around this is what Calif suggested, go water > fire > ice. That way once you cap water, it will stay capped regardless of what you do to fire, then fire will stay capped regardless of what you do to ice. The issue here of course, is that if you get water right on 15, but then accidentally get fire to 64, you have to feed more water to lower it. In this sort of situation, I generally cut my losses and start again, hoping not to overshoot next time.
However, the other challenge is leaking, where your highest element will lose about 1 point every 2 seconds (guessing), and the element weak to that will go up by the same amount. In order to stop leaking, you need to feed the element that is weak to that which is leaking. This means that if you do go water > fire > ice, in this situation, it will invariably be fire that leaks, and you need to feed ice to stop it. If you've already capped both fire and ice at this point, then ice will now be over target. If you don't stop the leaking (which sometimes isn't necessary, more on that later) then your ice will be continually rising as your fire is lowering.
So what you need to do, is keep both WR and leaking in mind when you plan your attack. One way around leaking (depending on the recipe) is to make the element you raise first be one where it doesn't matter if the weak element goes up. If an element is not required in the balance, it doesn't need to be 0, it can be anything. So for this case, you could start by getting earth to 30, to force it to leak rather than fire in the middle of your WR chain, but then you would have to leave fire below 30 until it does.
Let's assume then for a moment, that the recipe is actually 30 fire, 15 ice, 60 earth, 15 water. It would be quite easy to pump your earth up to anything above 30 first, then work on your water > fire > ice. When earth starts leaking, you can just ignore it to get the other three balances right. Because of the possibility of over-shooting, you only get one shot at getting these three elements spot on, so there's no point capping your earth perfectly if you're going to cut and run when you screw up your WR chain. Remember that since earth is now above 30, and nothing else in the recipe needs 30, that earth is going to leak anyway, so capping it perfectly is a waste of effort. Now, to stop the earth leaking, you'd have to feed lightning, which would lower your perfectly balanced water, so just let it leak. You actually don't have to stop leaking to complete the synergy, so having got your water/fire/ice right, you can now overshoot your earth, sit and wait for the leaking to bring it down to the target level and then end synergy. It can make it harder to get precise values, but HQ's are random as ***even with perfect values, and these rings don't have an HQ anyway.
So with all of that in mind, you have to really plan out how you're going to do it, the order in which you feed plays a big role. For the above recipe, I would start with water > fire, but not ice just yet. Get water to 15 (you can feed lightning to lower it, but if you over-shoot it by more than 2 or 3, just restart). Now feed fire until it's over 48. You can feed at 49, because an elemental surge with increased fire consumption rate will land you right on 60, but if you're at 50-60, an elemental surge will also land you right on 60, which could mean you're only getting a couple points out of it rather than the full 5-11. Remember, it's going to leak, so it doesn't need to be right on target. If it
hasn't started leaking yet, start on earth rather than ice. Most likely, if it hasn't already started, your fire will start to leak before you're done with earth, so leave it for now and start feeding ice. Your ice should be somewhere between -14 and -26 (unless you use smithing combustive smarts), but don't forget that it's rising as fire is leaking, as well as you feeding it. If the fire doesn't stop leaking immediately, your ice will be going up pretty fast, and could cap to 30 in as little as three feeds. As soon as your fire stops leaking though, stop feeding ice and cap out your fire. Your ice is about to go down a little more, so no point in capping it until fire is capped. Also, this is where you'll need to hope and pray, because if you overshoot fire or ice, it's back to the drawing board. With water and fire now capped, your ice is probably somewhere around 0-20, and earth about the same. Cap them both out, and don't forget you can feed wind if you overshoot your earth.
This sort of high level recipe will often need several attempts due to the unpredictable nature of synergy. Just stick with it, and don't forget to keep an eye on pressure/impurities and keep those down along the way. Even still, be prepared to thwack too, I've had explosions even with next to 0 pressure/impurities once the elements get high.