Woolwax is the best lanolin on the market today.I spray woolwax inside nearly every frame I repair. A simple spray gun at 70-90 psi is more than enough to move the product. You do not have to heat it at all. Just keep it above 50 degrees and you will be fine. If you need to thin it before application use/mix with vegatable oil, I use the 2 1/2 gal product, best way to purchase. The biggest difference between FF and WW is the odor. WW is nearly odor free, FF has a lingering smell that takes a while to disapate (I don't use this product inside doors, hatches or interior quarter panels because of the smell), WW is thicker than FF, both are lanolin based, FF tends to wash off quicker, you can purchase and apply a "thicker" WW product for frame applications (Creep n Crawl), anything you apply is useless without proper prep work, you can use any oil solvent to coat the rust but it will not stop the rust. Rust is the oxidation of metal exposed to the natural elements, oxygen and water chemical reactions) that has to be nuetralized before it gets corrosive and eats through the metal that is exposed. POR15, Chassis Saver, Eastwood Encapsulate and all other similar products just trap the oxidation and corrosion. These products do not stop the chemical reaction from continuing.
These observations are from "hands-on" use and application. I do not work for WW, I am not affiliated in any way with WW, but I have over 3 years experience using this product and never had any issues with it. Did I mention that the prep work done prior to application will dictate the end result??? (Piss-poor prep equals piss-poor performance!)