The idea here is simple. Greece leaves the eurozone (a Grexit) and returns to the drachma. Greece declares one drachma is worth one euro. They then print about $300 billion worth of drachmas (it would really just be electronic money for the most part, so the mechanics are simple). They use about $260 billion to pay off the ECB and IMF, redeeming all their bailout funds and technically avoiding a default as long as the ECB and IMF play along. Greece then uses the remaining $40 billion or so to recapitalize its banks so they can reopen and depositors can withdraw their funds freely. Greece’s remaining debt load is manageable with their current fiscal policy, so no major tax increases or austerity should be needed.
But, wait, you say, what about inflation? To avoid that, we simply need the ECB and IMF to leave the drachmas in their vaults. Then the money supply is only increased slightly and there will likely be only a moderate devaluation of the drachma, leading to “acceptable” inflation considering the alternatives. Since the ECB and IMF got paid, they do not need to declare a loss, or shortfall in capital. If the drachma devalues, they lose a little, but likely less than they would eventually have to write off regardless. Perhaps, they can sell their drachmas for euros slowly over a number of years, thereby avoiding placing too much downward pressure on the Greek currency.