best cover
is to make your spread look smaller than what it is by betting more than your ultimate minimum bet between the true counts of -1 and +2 (High-Low). In that count range just flat bet or randomly chip up and down using some nonsensical betting system.
The big tell for pitch games is spot spreading, so you if you start with one betting box stay with one betting box (don't spread to two hands mid-shoe).
The other approach that is effective is just to play numerous short sessions and take advantage of the fact that Vegas has a large number of casinos. Spread your play around town and play a lot of 20-40 minute sessions and then move to the next place never repeating play on the same shift and the same day. Be sure to download a copy of Stanford Wong's Current Blackjack News for a listing of all casinos.
Surviving at Double Deck is almost as much about where you play as how you play and as far as telling you where to play double deck, my suggestion is to play those places with lots of double decks and lots of action and avoid those places with only one or two double deck games or not a lot of action. If you're good at playing shoes and play for decent stakes you should not avoid the shoes...you'll get better rules (surrender), faster games, and better conditions.