Two Dozen Skip Loss Betting

 Start by betting $10 on the first and second dozen.  When you win just keep betting your minimum bet on each of the first two dozen.  

Skip Betting after a Loss
When you lose, skip betting until either the first or second dozen hit.  Then increase your bet up one unit to $20 on the first and second dozen.  If you lose again, wait until a third dozen doesn't hit and then bet on first and second dozen with 3 units $30 each.   

The goal of this system is to keep you from losing on a long streak of third dozen winners and for you to win on a streak of first or second dozen winners.  Even if the wheel bounces between the first and second dozen you will keep winning.  

Following a win at a higher bet check your string winnings.  If you are ahead go back to your base bet, if you are not continue on with the same progression.  

This is a very conservative negative progression.  It will keep you from rapidly increasing your bets in a negative progression. Your profit will come from winning on your minimum bet.  

As your bets get larger in the progression and you get a win, you will not win as much as you are behind.  The goal of this losing progression is to try to get you back to even so you can win with your two dozens bets.

Conservative progression $10 on each of the first two dozen, $20, $30, $40, $50, $60 

Martingale progression $10, $20, $40, $80, $160, $320 on each of the first two dozen.  With the Martingale you go back to your base bet after every win. 
This will eat up a bankroll very quickly with even a short string of losses.  However it will make money quickly if you bounce between a couple of losses and a couple of wins.

Winning at Roulette
You must win more times than you lose or bet more when you win than when you lose.  

When you bet on two dozen at a time you lose twice as much as you win, however in the long run you will probably win more often than you lose.  

If we knew when we were going to win it would be easier to bet more on the winning bet than on the losing bet. 

The reason you can win with a progression that gets larger after a loss is eventually you will win if you do not run out of bankroll or table limit.