My betting self would bet some money that tutorial would be ineffective. People that post here are quite capable of searching or doing anything else that may require much higher skills than searching.
People respond to incentives. Responses to incentives are predictable because people pursue self-interest. If we wish to achieve the outcome of not starting multiple threads on the same topic (clone thread), we are likely to succeed if we somehow make it against poster self-interest to clone thread.
Perhaps moderators make it too easy on posters by cleaning up after them. If somehow that extra work created by starting clone threads can be shifted from moderators onto clone thread starters, the problem would be solved. It is akin to expecting people to clean up the mess they create, not doing it for them. Cleaning the mess after someone else without any disincentive for the mess creator only perpetuates a lack of awareness, a lack of interest and a lack of responsibility for the mess creation.
It may not be possible to have posters clean up the mess on a site like this, but any negative incentive for clone threading or some other undesired behaviours may be effective. A negative incentive need not be large, quite the opposite, the slightest negative incentive is likely to be effective. It might be something like inconveniencing the poster by making him/her overcome some clicking hurdle or bombarding him/her with an appropriate message.
For a lack of a better solution, even taking away a single reputation point for clone threading might be hurtful enough for most reputation addicts to make them search before starting new threads. A penalty of taking away more than one point might be considered as too severe by some people
Others here may have some better ideas on how to disincentivise undesired behaviours in an appropriate, measured and workable way.