you can't fire off rockets individually in the newest version. this is something that I used to do... back when the rockets were configured more like the original CFS3 game.

I try out the planes I want to shoot down one in free flight. I put it on autopilot and jump in the observer's chair and swing the gun through the entire radius of motion and try remember the blind spots.

I don't avoid attacking two-seaters unless there's nothing I can meaningfully do to them. shooting down two-seaters is the whole reason that fighters were invented!

RAF_Louvert's linked method is solid. it's actually what I generally do when I attack the Roland C.II on any flight simulator. his technique is useful because he's attacking from slightly below and in front. because of the placement of the aircraft's engine and wings this is a blind spot for MOST two-seater pilots. just as importantly, it's a blind spot for their machine gunners as well. for the Roland, it's a really bad blind spot. so it's just about perfect. the DFW has a pretty long nose. so don't be surprised if those two-seaters don't even realize they're being attacked until bullets start hitting them.

that being said... I wouldn't recommend this specific method when attacking the FE2b or the Caudron G.IV!

one similar method of attacking two-seaters/bombers that I've used in nearly every flight sim is this:

it's basically a dive-bombing style attack using machine guns. approach enemy formation from above and in front. you should have about 2000-to-4000 ft worth of altitude advantage. dive down at about 45 degrees and reach maximum safe speed. point your nose about 100 yards in front of the enemy and open fire so that within a fraction of a second the enemy will fly into your bullets. gradually ease up on your descent angle and start leveling out. the whole time your gun should be firing at the engine. you could try to aim for the pilot... but with this method of attack the engine gets more reliable results.

your combined closing speed should be very fast. if you level out slightly below and in front of the enemy you'll still have a lot of residual speed built up from your dive. if the enemy turns to attack you then you can keep diving and create a huge amount of separation. the other option is to zoom-climb with your remaining energy. if the enemy flies on straight then you can assess how bad the damage is. if you've damaged somebody badly enough to drive them out of formation then go in for the kill after they'e fallen behind. if enemy scouts have shown up then you might have to settle for merely scaring those two-seaters.

against planes with large blind spots in front... this method is great. I wouldn't advise it for the FE2b or other planes with free-mounted machine guns on the bow. in those cases the best thing to do is to attack from below and behind.