Not an AK but...
I recently bought me a Yugo SKS with grenade launcher and needless to say....Cosmoline everywhere...
Simple green worked but took to damm long..
And then I saw the solution....A DIY car wash....Hi pressure washer
I took the barreled action first so it won't draw the attention of holding a complete rifle and set the wash cycle to hot and soapy...3 minutes laters...NICE and CLEAN metal...Stings the fingers..
Second trip I took everything else incliding the stock......
The stock only needs some wood oil to replace what the detergents removed...Cosmoline
5minutes later....All clean and no cosmoline...A lite lube and ready for the range..
Use good judgement as to where you do this....I did mine at a low traffic time and area...
It only cost me 6 dollars and a vacume because the wife said so.....