We use the WD40 in the Fall when the Cockleburrs get real bad. You can have them look like they hadn't been brushed in months when in fact you brushed them out yesterday! The WD40 gets them out faster. But just for regular detangling I use Infusium 23 you buy at Walmart and dilute it a little so it lasts longer. Or Mane and Tail Detangler. But I think a lot of the horse products have silicone in them which drys the hair out and causes breakage. So I am also a fan of Shapleys MTG because it is oil based.
I DON'T LEAD 'EM AND FEED 'EM, I RIDE 'EM AND SLIDE 'EM.