I tho't I would throw in my 2 cents. Here are some of my favorite manuevers. If run into resistance from any one; try to find out just what there policy is. 2 to 1 odds are you won't get the exact same answer from any two employees/dealers or pit bosses...
Recently, I was at the TI in LV, apparently known for their tight policy in selling chips that are not put into play. Soooooo....here are some of my favorite ploys:

Big Six wheel (usually always uses single dollar chips) when it has a dealer. Ask for 20 or whatever amount. Then have your wife come up and call you away. Or if operating solo; suddenly remember something that requires a quick exit.

Blackjack Tables: if they are $5 limit or higher tables...they usually won't sell you a large amount of singles, so try for $5 or $10 instead of $20.

Craps Tables, when idle are always an easy mark to get twenty, if slightly busy it is still pretty easy, timing is every thing. (they have usually 3 dealers)

Roulette Tables when they have dealers will usually sell you up to twenty, idle or busy.

Cashiers, definitely are regulated to house policy; however that varies by each individual casher. They take breaks, have shift changes. I went back three times at the TI got 7 chips, my wife went up to the cage and got 5 in one shot. I was told by the floor Supervisor that 2 is the limit per person.

If you are with a group, line them up at the cage...

Hope this helps....

Reggie