Deburr the block & heads. Use a file/deburring blade/die-grinder on casting-flash and sharp edges. There is often quite a bit of casting flash around oil drain passages.
If you don't have a set of engine cleaning brushes
, get some. (About $30-$40.)
After washing the block, I use paper towels and ATF (auto trans fluid) to wipe down the cylinders and bearing journals.