Ive never had the left side off & dont know how the oil runs in there,,I dont even know what spins over there & how much oil is there or how any metal got from there, into the oil, but it did,, so, theres gotta be oil passages. From the clutch side, theres several openings so you can see up in the sump,
What to use,, Id start with a clean rag on a wire with a loop in it & mop out everything I could,,


You know,, really,, how about this. seal it up, put a little oil in it,lean it back & forth some, not layin it over enough to put crap where it hasnt been, get the rear end up & let it sit for a few hours, let the crap slip down to the front, gonna need to get the rear end up pretty good to do that,,if the tanks full,, drain some off, Thats not aluminum you ate, is it?

If you have a really serious magnet, you could work it from rear to front, on the case, sweeping the metal inside. Ever seen those magnetic aquarium cleaners?
Then drain & see what ya get.

Its taken me several ideas to finally find the easy way to clean up the case on mine, you may try a few things before ya find something that comforts you..

What did ya find in that oil filter & did you see sparkly stuff on the outside of it?

IDK just how clean it needs to be before its safe to run it, IDK if ya hurt it, or if the transmission gears are gonna be chewin & trying to digest hunks of crap or if what you did just created small filings. Im hoping theyre small, but not so small as to slip thru the filter.
Id clean the bottom emd till I got something that looked good back out, then fill it & run it for a minute or 2, then drain & see what come out,, just use cheap oil, & no need to change filters with every drain after run until youre ready to put good oil in & ride. You can tape a magnet over the oil window & look there. If you start seein crap , drain it.
& it wouldnt hurt to check out Old Fellers magnet in the oil filter & a magnetic drain plug,

Wouldnt take it apart,, youll be okay,, Ill bet the filter has done its job & youll sweep most of it out, Its hurt, its life is gonna be shorter,, but how much? Instead of 100,000 miles, only get 65? Just change oil frequently for a while, keep an eye on the drain plug magnet,, Its always gonna have a small beard, mine always has,, gears wear, stuff like that,, dont panic, just flush it a few times, you can do that while it leaks,,

I hope I havent sent ya wrong,, its what Id do, & change oil early a time or 2,, Id dump it after 50 miles & have a look, for sure, Its okay to run less expensive oil some, once ya get it so you feel good running it, then toss the good stuff in,If you dont get much crap, dont change the filter,.