It is not time consuming to have GTC limit orders to buy on weakness or to sell on strength each member of your portfolio.

FORBES: Apple's Cheap But Intel, Cisco, Dell are Cheaper

The ETF Trader provides Value Levels at which to buy on weakness and Risky Levels at which to sell on strength for twelve index ETFs, twelve sector ETFs, two emerging markets ETFs, one fixed-income ETF, and three commodities ETFs.

FORBES: Traders ETF Strategy

Lately you can buy on the lows of the day but anytime you add on strength it has not been rewarded.

FORBES: Stocks Rocking To New Moon On Monday