Lots of great recommendations here.... but I'll add a silicone based lube for her feet. Uberlube is a great product. You can find it on Amazon by name.
I have used many oils, lotions, and sports "anti chafe" sprays and sticks in the past on different women. For whatever reason... Uberlube has an extra effect to it that trumps all of the above "slippery sole" products. It's just bananas. Takes what would otherwise be a 10 to an 11 or 12.
Also... the gloves for brushing pets with the little plactic nubs on them are devastating in combo with the Uberlube. As well as the massage gloves you've previously mentioned.
Another tool, tho not as devastating as the above, is an anti-tangle / detangling hair brush. The bristles are a little stiffer and closer together. But Ive found that the standard hairbursh works marginally better than this.
Don't go into this without Uberlube man. Trust me. Use this over any lotion or oil. It's awesome stuff and I wish we saw more vids using that instead of baby oil. Slippery as fuck and it lasts longer.
In fact, if it were me, I'd skip all the oils and lotions and just go straight to the Uberlube when it comes time to get her soles lubed up. It will give a much more intense effect bc not only will it go from a sudden "dry tickling" to slippery tickling, but also have that extra Uberlube effect. Imagine her face and thoughts if you suddenly put lotion or oil on her soles. Now imagine that with the Uberlube. Trust me. Make her 1st out of her mind ticklee experience count, and use it wisely my friend.
When's the set date for this? You gonna make a vid? Let us know how it went! I'd love to hear about how the Uberlube worked for you. Also would love to see and hear how it worked, but at least hear from ya about it! She's got some really nice soles.
Have fun buddy.