always the garage kit option will have these, with revive series on goin, bandai most likely release common use weapon series...

so expect to mix match iron-blooded orphan series weapon la...
general purpose thinner (GP thinner), mineral spirit, lacquer thinner all can do the same cleaning job but difference is on how strong it is.

normally for cleaning kit parts i would recommend lacquer thinner coz less corrosive on the plastic, other options are strictly for cleaning other stuff
totally agreed, went there a few times during my working hours also can see them open... and thought closed them forever...

If just for cleaning tools, any thinner from those roadside hardware stores will do
Around 5 bucks aje