Is there anything that would be a good substitution for thin lube?
Trumpet valve oil?
Sure. I’ve also had good results with sewing machine oil.
I use valve oil to and have great results, but when you put it on use a pin or safety pin and put a drop of lube on that and then touch that to the bearing in a few spots. Then spin it with your finger to work the lube in. This video will help lots to: http://yoyoexpert.com/forums/index.php/topic,871.0.html
Playing a bearing dry will kill your bearing faster than if you lubed it. Companies saying play it dry actually sell bearings so they want you to buy more when you kill it.
this would be more like thick lube