After 17 years of 'oil' undercoating with Fluid Film and other 'oil' products, (5 years done professionally / 12 years DIY touching up),
there are areas on my vehicle that are sooo oily, I'd be embarrassed to have a Mechanic do any work on it. They may even refuse.
On the rare occasion a Mechanic does any work, I take it to the Car Wash and hose down the area.
Don't get me wrong, Fluid Film is great stuff (it creeps),
I believe the WoolWax that OP refers to is a thicker version of Fluid Film.
I recently purchased a case of Cosmoline in aerosol cans.
Fluid Film vs Cosmoline - Both have pros and cons.
From now on, any 'new' replacement parts will get the Cosmoline.
Last Week I washed off my Rear Axle/Diff and sprayed with Cosmoline.
Ideal situation - Several years of 'light' oil undercoating.
Then, transition to Cosmoline.
Don't over-due the oil like I did.
Oily Mess
Cosmoline (the Gentlemens Undercoating)