I am about to put my two cylinder heads back in and did some preliminary finger fitting of a bolt in every one of the 16 shafts to make sure it goes in smoothly, i.e. no gunk/debris impeding the fit. As it turns out, all but one are fine and clean and one is not quite. I can twist a bolt all the way in to the same level of the bolt only using a ratchet but not with fingers and it feels like there is something like residue or a piece of gasket maker inside. I tried blowing it out with an air nozzle (which is what I did with every other one anyway) but that didn't work.
Should I use a metal tube/pipe brush like this? I am concerned about a string falling off and staying in the shaft, which would then jeopardize the torque.