I thought the OP should have gotten a lot of answers and also found a solution to his question, in fact you are quoting his post after 5 months since he created this thread.
Since I signed up for forum account until now, I don't think I'm too interested something free like airdrops or anything else. Even I had to forget about the bounty part which is actually still productive until now, but I'm too disappointed with that part. I think a lot of people should be prepared for the fact that expecting something free is ultimately a waste of time, but of course every now and then some people are also lucky enough and make a decent amount of money.
Indeed in some stories and news I've heard Airdrops can provide attractive prizes but maybe it's only one in a hundred airdrop programs, so it seems like luck alone to get that. That possibility is still there but I agree with what you said.
So it may not be very effective to hope on an airdrop or follow a bounty program. Maybe you will feel tired because it is quite difficult to get an Airdrop or bounty program that provides prizes that have prices according to the work you do. There may be other than that like doing a roll, on some sites. But the prize is too small and there is a minimum requirement to withdraw. In the end, there is nothing completely free to get bitcoins.