What liquid flux to use with Bon Pen?

[zapta]

I ordered a Bon Pen and need to get liquid flux to fill it. What kind should I get, no clean? rosin? RMA? RA?

So far I used the ChipQuik tacky no clean but it is too thick for the Bon Pen I presume. I also has a felt pen with Kester 981 and it kind of works but the flux feels weak.

If I get a rosin based, what happens if I don't clean it perfectly, for example, under the components? Will it corrode and damage the board?

This is for hobby use at home. My components are typically new, I use leaded solder and I clean with IPA. I want to have just one kind of flux, even if it is a compromise.

[ConKbot]

RMA flux is good for applications where you might not be able to clean it. RA is a little too active/aggressive.

[zapta]

RMA flux is good for applications where you might not be able to clean it. RA is a little too active/aggressive.

Does this look good?  I need only a small quantity and this US seller seems to be legit.

http://www.ebay.com/itm/141250481358