- just make the function / class you're working on nicer, preferably just a small function. Apply some common quality standards to it, clean code, nice docs. - repeat this for a while, and you will have a nice set of examples and guidance for the other team members by setting an example.
Personally I am a huge fan of making that one place where you found the bug nice, adding a simple test case and moving on to the next thing. It adds up over time and does not hurt in terms of time involvement/budget since you already had to invest a larger amount fo time to find the place bugging out.