I can't speak for R and Sec. lines, but:

going into training: try to put max trips after training start. If training starts beginning of 3rd week of the bid month, try to get a line that has all the flying after training start date. Check contract for rules if training starts mid-trip or conflicts for what you owe them.

during training (full month): max CH w/o c/o

Leaving training (partial month of training/IOE and custom line): Bid max days off line with the most pay. Your custom line can't give you more work days for the month than the line awarded regardless of CHs.