As of recent I notice the PCB "no clean" stuff is everywhere. However, many-most of them are more difficult to clean off vs RA or RMA rosin fluxes.

That said, can anyone recommend a decent RMA that can be used with a small soft bristle brush?

 

This Kester pen is a very convenient way to apply flux. But no clean flux… doesn’t have to be cleaned.

 

Thanks for the pen link.
I doing some Rf boards, I need to clean them good. No-cleans seem to be more a pita to clean.