What you're really trying to do is to tempt your opponent to put their nose up high in the air, AND, critically, pull lead over and above that in order to pull the requisite lead to get the guns solution. As long as you have more E (either by way of not loosing it as fast as your opponent due to a better sustained climb rate, OR, you simply start out with more) and your opponent is pulling lead (in lead pursuit), they will find it difficult to hit you and will run out of steam before you do and drop away. Remember lead pursuit costs more E than pure or lag pursuits. Its at or around that point you will need to be able to convert your E advantage to a positional advantage for the kill shot. If you've set it up right, a quick kick of rudder in the direction of your struggling victim and bit of aileron will kick your nose over and down at your victim for the shot opportunity.
Normally i like to 'profile' my opponent in this move. To me, this means, looking almost straight down the inside wing at my opponent. The inside wing 'points' at them. If they get too far around to your rear, then you know they may have a shot. Keep an eye on the profile of the opponent aircraft, if you can see a side profile, you have him home and hosed, if you can only see a front profile or a front-quarter profile you know they probably can take a shot or are not far from it, so it may be best to re-evaluate your options at that point. There's always constant evaluation required, both in the decision to enter the spiral climb (eg do you know you have the requisite E advantage and/or climb advantage to make it work), and in the actual execution of the move, and the follow-on end-game/bug-out.
Spiral climbs are risky at best. Even if you get it all right, and correctly estimated relative E stakes and factored in sustained climb rates, and know where the bug-out point will be for you, and you've set him up perfectly, and you manage to stay out of their guns, and they dont do something clever like a low yoyo to counter etc etc, there's still the chance of missing the follow on shot, in which case a second spiral attempt may be foolish, or someone else will just come along a cherry-pick you as you are slow at the top of your spiral. 1 20mm/30mm hit can really ruin your day too...
Some aircraft are better at these sorts of slow-speed climbing contests than others even if they have an inferior climb rate. Good example is the P38 with its counter-rotating props is extremely stable at slow speeds and doesn't have any nasty torque effects to snap it into a stall that single-prop aircraft do. Also remember to climb in the best direction for your aircraft - left for most aircraft. Tiffies, tempests, yaks, spit 14 actually turn better to the right, IIRC. That is also useful to know if your trying to spiral climb against a tiffie.
