What is the best strategy to use for those "remainder" troops from when you attack a 2 with a 3 and sometimes you are left with 2 in the territory rather than 1. What is your strategy for consolidating these troops?

Use them as order delay moves, just move them around before you attack when you want the attack to happen last.

Yes most likely order delay often you will also want to take a bonus where you can use thoose armys for next bonus ... (picking a territory in start with good expansion around it)