Solder Flux Removal Question

[UnFocused]

I just replaced all of the MX brown switches in a QFR with vintage MX blacks and everything is working as it should.

I'm a somewhat new to soldering and I used a bit of flux on several switches from a Kester "Soldering Flux #186 RMA FLUX PEN". I tried cleaning the flux from the PCB with 91% isopropyl and a not so stiff anti-static brush, but now there's a sticky residue all over the PCB. I don't think the alcohol was dissolving the bristles of the brush because they look normal.

Wikipedia tells me that "RMA flux is formulated to result in a residue which is not significantly corrosive, with cleaning being preferred but optional."

So, while I don't think I NEED to clean it, should I? Will leaving the sticky residue on the PCB cause problems down the road?

Exactly what product should I use if I do clean it?

Also, these vintage MX blacks (from a Wyse board with what looks to be a 1989 date code) are wonderful!

[jcoffin1981]

I see many circuit boards with the residual flux still left on.  It's non conductive and non corrosive.  A thick solder paste I would probably try to clean the excess.  I am not the authority on soldering, I'm simply telling you what I have seen and in my opinion it's not a problem.   

If it's liquid flux from a pen you could simply dab it with lens paper or a tissue and soak up most of the remaining flux.