You should only really give Player Instructions (PI) to make the tactic more fluid or give it an edge. This should be to main players in the tactic, and not just at random. For example, if you want to create a more advanced playmaker that is a left or right winger, but play a 4-4-2, then you should imitate the PI of a normal left or right winger in a 4-2-2-2, 4-2-3-1, 4-3-3 (etc.) into the 4-4-2, thus making him more dangerous.
Or, you can just play to their attributes. If they are poor at long shots, but good at crossing, make them cross better to the target man onto the near post at the byline and put down their long shots.