25 ...resigned
Game 624856
Thanks for the advice. I set up a board without the pieces (assumed all traded), and Black's strategy must be to use the King to stop the pawns. But a better strategy is to resign. So i'm close now, but think there may be something still to learn.
Nf6: save the knight (maybe for tripled pawns), but the White knight can attack the corner in one move. Also, my knight already guards the likely Queening square, so why move it?
Rd7: followed by Nc7 ...QxQb7, axQb7, and the rook blockades the pawn, and white wins by bringing the rook to a8
QxQb7: this seems most direct. and leads to: axQb7...Rb7, Rb1... after which both knights take 3 moves to cover the b-pawn, and White wins a piece.
Now that I've gone through all this, it is time to resign.