Today, I was playing Holst's Second Suite in F (Movement 1) on my Flugelhorn. It sounded great, but I feel that some particular sequences are a bit muddy in the fingering. I usually play with the middle of my fingers rather than the fingertips, is that the problem? What would be the proper way to finger these awkward sequences?
Unfortunately the design of most piston-valve flugelhorns encourages that kind of playing technique, but it really should be avoided if possible. Actuating the valves with the middle of your fingers actually makes you work a lot harder since the movement of the tip of your finger is amplified as though it were a lever over a fulcrum.
You should try to keep the same posture fundamentals on flugelhorn as you would on any other bell-front valve instrument:
This does take a bit of finger strength, and you may have to adjust things for certain hand sizes or instruments, but the basic tenants should stay the same: keep the fingers curved with the fingertips resting on the valve buttons, and don't add unnecessary tension to your posture, grip, or technique.