One of the best ways I've found to learn to play better in tune is to play with drone tracks. I don't like using a tuner, as it doesn't really accurately represent where the pitches need to sit in each key. An E in the key of C is not the same as an E in the key of F! Secondly, tuning is an aura skill, not a visual one! Looking at the tuner won't help you when you don't have one to look at ...
I usually have students start with the major scale and go very slowly to practice tuning each interval, and then speed it up slightly, to practice tuning pitches that move by more quickly in a real life situation.
Practice this very slowly! And be patient. Get each note to resonate against the drone track. If you can get the track playing at equal volume on some speakers, that would be ideal! But, headphones can always work in a pinch. Make sure you keep one ear off, so that you can hear the pitch coming from the drone.
Playing in tune on a brass instrument is a constant battle, so don't give up. It's always good to go back and try to improve your ear!
Good luck! Please don't be afraid to be in touch with any questions.
See ya next time -