I am looking for the procedure and what, if any, triggers can replace it.
I'm also curious if the cheapo Shadow 1000 can be tuned so that that godawful twang wouldn't be so "rude".
is to apply some grease to the mainspring. Not a whole ton, but certainly more than just a thin coating. When I've done it I've applied enough excess to cover the outside of the spring and so that there's been a little of it between the coils here and there. I've done that to three Gamos and it's pretty well eliminated the twang. I'm not a fan of tar, but there are probably some here who will argue for it.
As to the trigger, I know I've seen some diagrams online, including here on this forum, so look around some and you'll see it eventually...or someone else here will link you to the string.
Have fun tuning.