What? First Not sure why contact enhancer would do anything accept dissapate like Flux once you hit it with heat and the solder actually would just clear it and adhears to the metal component directly most likely just pushing the contact enhancer out of the way or turning it into fumes...
Unless when you use a silver solder like WBT etc... When you apply it the gold and it actually melts and mixes into the solder while wet and gives you a gold solder connection sheen instead of bright silver?
I really don't see how this is of any benefit to a connection before or after soldering said connection. I have not tried it so maybe the treament simply melts and mixes into the solder while its liquid metal, and the gold is really that much better than the silver in the solder, don't know, but maybe the explained method here is just not making any sense.
Contact enhancers normally are to be used in order to lubricate and "Enhance" a connection point that is not permanently fixed by solder at all.. Such as the pins on the power cord to your wall giving the unlike metals in your outlet and your power pins a conductive liquid barrier due to mechanical movement and fit keeping it with full current flow and contact even if its a bit loose or not totally tight contacting all surface areas of the metal connection.
I have used it on Quick connects inside the speaker however where the cheap TIN spades on the drivers could use a good corrosion preventer and liquid conductive material without having to Fix the connect permanent with solder.
Your better off Sanding or Steel wooling your Crossover parts leads to break down the coating and then solder if you want a more prepped or clean joint, I just don't see the benefit of wasting a 100 dollar contact cleaner/enhancer on this joint and soldering it after. Again most likely if somebody does here an "Enhancement" from this, its most likely due to receiving the crossover parts and not cleaning them before solder, in turn simply applying an enhancer at more expense to give you that cleaner lead to solder.
Not arguing just don't get the reason, use some sand paper on the cap and inductor leads and probably get the same results, or just buy a solder with some gold content in it.