I figure not many people carry-on-only for international flights.
If you do only carry on for international flights and plan to just check in on-line and print a boarding pass, be sure to check with the airline to see if they have any security questions to ask.
They will sometimes have questions to ask and if you try to board without their sticker, you will be turned away. Even if you went through airport security. Oops.
I haven't shipped to 'wherever', but I have shipped stuff home when I am finished with it. Hasn't occurred too me to ship fuel. I have bought fuel or rubber mats and then left the remainder behind on the share shelf at a campground. Remainder of fuel. Mat was in one piece.
Oh, everything I take is about the same color. gray, tan, sand, etc. I suppose it would be the same if everything I wore was purple, but that would be weird. Wearing tan and gray is probably weird. No colors makes things easier to wash. I do the laundry thing... Have washed a couple shirts in the shower with me at the same time. Worked well enough. Never used a sink.