If you're not taking the rod apart all the time...wrap a couple of layers of tape around each joint so any imperfections in the joint don't scratch up your barrel. You can also place of peice of partially shrunk heat shrink over the joints.
Your cleaning rod is for cleaning (d'uh) and as such it should itself be clean (d'uh again)...but A LOT of guys don't bother to wipe down the cleaning rod before they stick it down their barrel.
DO NOT use the pull type cleaning strings...that'll mess up your gun. Also, you should ideally turn off your hopup all the way before pushing a cleaning rod past it.
I'd aim for plastic vs. aluminum... Lots of building/hardware stores have
different material...Might be worth taking a look there for a cut off piece (which they'll often just give you).
Aside....Inner barrels are 6.00-6.10mm...usually 6.03 or 6.04mm for tightbores. 6mm translates to .243 cal. However .22cal rods...even if they list that they're really only for 0.22-0.25cal barrels..are more prevalent/cheaper. If you use a .243cal rod with thick patches it might be a really tight fit.