Defense against Artillery Spam?

Situation:

• It's been a few months since I've last played so I'm a bit rusty
• I remember my favorite strategy was a resource boom (made easy by Portugal's free Covered Wagons increasing Settler output).
• I put some minor thought into my prior strategies and I feel the best strategy would be for me to add a bit of improved turtle tactics to my boom strategy since my largest problem was getting attacked before having troops.

I understand the nature of a boom-strategy therefore I'm not here asking how to prevent getting rushed, I know some tactics on that but inevitably the only acceptable way is spam walls or build troops.

I specifically play Portuguese but I'm open to any tips.

Question:

How do you defend/turtle against a well-done enemy artillery spam?

Attempted Strategies:

• I've tried lining the inside of my walls with my own artillery. This either ends in my artillery getting shot instead of the walls or the enemy shooting walls at max range and then going for my artillery.
• Lining my walls with a mix of troops which unsurprisingly yields similar results.
• Sent troops out and attacked. This seems to work about 50% of the time, the bad 50% ends with another anti-(insert my troop-type here) force picking them off as I attack.

Obviously a decent portion of this is failure to micromanage but ignoring that portion are there any decent strategies that would help me promote my Boom/Turtle strategy? (Allow me to defend my base with the combination of Walls, Outposts, and a small troop force? I do my best to keep my build HP upgrades coming while keeping my troops strong too, but obviously until late-game (where I destroy everything) I am primarily focused on economy boosting.