There will be some filler in Mike's 1,4 caps. Rice bran, I would *guess*. Not exactly sure how much, as I don't think I have anymore of the 300mg caps here, so I can't weigh one.
1,4 is definitely soluble in 99% isopropyl alcohol. If you use enough, the 1,4 will fully dissolve, and the filler will eventually settle out of solution. You can then filter it.
It's not really a difficult procedure, but I really don't recommend it with 1,4. The oral bioavailability is just as high as the topical absorption will be, so the only advantage of the topical is the inherent time-released nature. If you dose the oral often enough, say 4 to 6 times per day, you should be able to achieve fairly constant blood levels.
Not sure what dosage you were planning on taking though. This is one reason why Mike's 200mg caps (which he now sells) are better than the 300mg caps (which he no longer sells). You can dose the 1,4 more frequently with the 200mg caps, without having to take your dosage level too high.
If you are dead-set on using the 1,4 in a topical, you can also just purchase the bulk 1,4 powder from Mike. Then you avoid the whole dissolving/filtering procedure with the caps. You can always save the caps for a future cycle then, as 1,4 is an excellent oral PH.