Basic DL/DR training guide
What you need:
2-3 star fast trainer DL/DR of your choice, about 400 rests to spend, about 1h of time, for best result max training level
What you want to do:
Train every of the below following drills to an average of 120%, then change the drill.
(Calculate average like this: Average Gym = (174% Fitness + 109% Strength) / 2 = 141,5% ... so value of every skill of the drill divided by number of skills of a drill)
Drill order:
Carioca with Ladders - Hurdle Jumps - Press The Play - Defending Crosses - Set Piece Delivery - Gym - Use Your Head - Slalom Dribble - 1on1 Finishing
For my particular player I needed 380 rests to get him from 38% to 133%. These are 4 rests per overall %. After the training the average of the white skills relevant for a DL or DR is 175%.