Every few months I get large commission checks (in the 20-30K range). I invest at least 75% of these checks into my cash account. Sometimes I use 25% or so to pay down debt (we don't have any debt now except the mortgage -which I'll never pay down!), go on vacations, pay property taxes, etc... I keep all my cash holdings at Vanguard (except my checking account!) Once the check is in my checking account - I log on to Vanguard, click on the Portfolio watch tab and look at how a hypothetical trade impacts my AA. Then I transfer the money electronically to Vanguard. Essentially, I use the new $$$ to keep my portfolio in balance throughout the year. This is a tax efficient way of re-balancing because I don't have to sell anything.
Re- DCA vs Lump - I don't wait. I lump it in. I'm a lumper - I've DCA'd into the market in the past and always regretted it. I figure that 2/3 of the time the market goes higher, so why fight those odds? In fact, later this month (on Monday the 25th) I am getting a very nice commission check, it will be fully invested by 26th or 27th at the latest. I suppose if I received a one shot inheritance I might re-consider my lumping strategy, but it'd have to be a really large amount of money (minimum of over 500K). In that case I'd lump half right away, put the rest in a MM fund and DCA over 6-12 months.