Can Black capitalize? I have played a game against a computer and came to the following position:

[Title "Black to move"]
[StartFlipped "1"]
[fen "3q2k1/pp1r1p1p/2p1p1p1/2Pr2P1/P2P1P2/4Q3/1P1R3P/3R2K1 b - - 0 1"]


I gave my best to capitalize, but in the end game was spectacularly drawn (3 queens were on the board at some point, but I have managed to save myself with perpetual check).

I feel sad because I believe that Black should be able to win the game from the position above.

Can you demonstrate a winning plan from this position?
After 1...b6! Black can win a pawn. Whether that will be a winning endgame or not is a different matter, but I don't see a better plan for Black. So 1...b6 looks like the most reasonable way to pursue a win. 

[FEN "3q2k1/pp1r1p1p/2p1p1p1/2Pr2P1/P2P1P2/4Q3/1P1R3P/3R2K1 b - - 0 1"]
[White "Comp"]
[Black "ALNS"]

1... b6 2. cxb6 (2. b4 a5 3. cxb6 axb4 4. Rc1 Qxb6 5. Rc4 b3 6. Rb2 Rxd4 7.
Rxd4 (7. Rxb3 Rd1+ 8. Kg2 R7d2+ 9. Kf3 Qd8) 7... Qxd4 8. Qxd4 Rxd4 9. Rxb3 Rxa4
10. Rf3 Kf8) 2... axb6 3. b4 (3. Kf1 c5 4. Qe4 cxd4) (3. Rc2 c5 4. Rc4
cxd4) 3... c5 4. bxc5 bxc5 5. h4 cxd4