I carry a small (4 oz plastic bottle) of 75/90 gear oil, a very small can of WD 40 and a 1 inch cheap paint brush. These don't take up much space, less than the size of a can of chain spray and I can make these supplies last for a month on the road, if I'm careful.
To clean the chain- spray the wd 40 on the brush and rotate the wheel (I have a centerstand). One spray on the brush for each side of the chain. Then wipe off the WD 40 with a paper towel.
To oil the chain, use the same brush, only put some gear oil on it. Same routine, hold the brush against the chain and spin the wheel. Again, wipe off excess oil with the same paper towel.
When I'm traveling I do this everyday, usually in the morning but almost never when I should do it: at the end of the day when the chain is hot.
When the day's riding is done, it's beer time and I forget all about the chain.