What are some tips you could give me on lubricating a Dynorbital sander?
Dynabrade recommends a 1 drop per minute setting when using an F-R-L (filter-regulator-lubricator). If this is not feasible, it may be best to: 
1) Place 2-3 drops at the coupler before using in the morning
2) Place 2-3 drops before using after lunch
3) Place 2-3 drops at the end of the day. After the last step, run the tool for 20-30 seconds to distribute the oil in the air motor, then it will be fine to let it sit overnight.