Hi iirwnn,
Strengthen questions and Assumption questions actually have a lot in common - so most of the 'steps' that you would go through to answer Assumption questions can also be used to answer Strengthen questions (the ultimate difference is that a Strengthen question requires that you do one additional step - find an answer that strengthens the logic/assumption(s) that the prompt is based on).
If you're having trouble differentiating between those two question types, then you might need to train with some new practice material (and learn/practice some new Tactics).
1) How long have you studied for the GMAT?
2) What study materials have you used?
GMAT assassins aren't born, they're made,
Rich