If a random country is in debt, is printing money a good way to pay it off at the expense of the citizens?
For example, lets say you owe an entity $100. If you print an extra $100 bill you pay off your debt, but unbeknownst to the entity the $100 that they lent you is now worth less.
Would the barter system be a good way of combating this?
The answer is "Only if the velocity of money is decreasing".
The velocity of money is the rate at which the money circulates. So say you get a loan from the bank (so money is being created with the loan), then you spend it on a car, that money goes to the salesman and the manufacturer, they in turn spend it on their mortgage and so on, and the money circulates.
The faster the money circulates, the greater the velocity and the greater the tendency to lead to inflation. In cases like that, the central bank will raise interest rates, to deter borrowing, and the whole cycle will slow.
If the velocity slows down (people arn't borrowing, and the money they earn is used to pay down their debts, this destroying money), then you can print money without causing inflation.
But if you print money while the velocity is high, then you end up like Germany in the 1920s or Zimbabwe now - with triple digit inflation.