the very tightly rolled up foam keeps the liquid from spilling when it gets knocked over in the tent.
if you spray benzoin on your foot, goodness but it goes all over, and thence onto a very expensive sleeping bag. yuck.
deodorant roll bottles drool and what fun is it rubbing a hard ball of plastic into an open heel wound. they also tend to not seal very well (poor cap integrity)
swabs leave you to deal with a dead .. swab. (and it's wrapper)
some folks even swab from a bottle, and that looks like a DISASTER about to happen.
thusly : we went on the prowl for a way to dispense sticky liquid sans the danger of messing the tent, and consider that there is a limited amount of this precious fluid on the trip too.
this was the whole bpl dogma .. a long line of possible bottles set on the counter, notes, tests .. all the anal bpl'ish routine.
they all failed in on way or another, except the foamy thing. which just kept working better as it developed over several iterations.
if one rolls enough foam and thrusts it into the nalgene bottle, it dispenses benzoin optimally nice. and yet, when knocked over, gives you a few seconds before it (slowly) begins to drool. the foam (which sticks out the top a little bit) is nice and soft on open wounds ( plus, the alcohol cleans as it goes), and you have good control over covering the area you're aiming at. the nalgne cap is substantial enough to generate a reliable seal.
when making a foam bottle for benzoin, DO NOT try it out first with water, and then add benzoin. water and benzoin will not happily co-exist in there. if you pre-run your device with water, remove the foam and dry it out 100% totally before reinsertion.
i suspect the service life of the rig is about 3 years, as the benzoin does seem to marginally attack the nalgene material over time.
1oz looks to be plenty enough, even for a thru hike.
i am using the Smith-Nephrew benzoin, and it seems optimal. there apparently exist stronger adhesives such as Mastisol and H-Tac, but i'm quite satisfied with the adhesion of the Leuko-P / Benzoin combination. it's right where i want it to be as far as durability when wet, and still be removable.
peter has had quite a few demons with foot blisters and they have cost me not only tens of thousands of dollars in ruined trip costs, but far worse, Several Years of lost opportunities (when trips end early).
in 2010 i stupidly changed insoles and developed an issue where the heel bone actually "came out" the back of my foot. you could see stuff moving in there it was such a nice wound. (it cost me a year, and i'm already 60. so see, i don't have years to lose ). since then i have taken the foot care - tape- benzoin situation MUCH more seriously. thusly, the foam filled bottle !
thank you for your question. i hope all that puts an end to any blisters you have, as it has for mine.