Here is my trophy guide
INTRO
This video was made with the intention of showing the way I did my run for those who want to see it done from different perspective. Keep in mind that other than the boss ramps themselves, your seeding will be different than mine but the style and approach (and timing) are generally the same.
NOTES
1. Bike style: TJ DH12 (most stability)
2. Crew members: you can have up to 10 crew members but it's not recommended for this trophy as it gets harder over time and the point is to finish without bails so you want to play the minimal amount of races as possible. But because you can unlock 2 within the first 1-3 races, I highly recommend restarting your race if you don't get "Landing Impact", "Smoother Curves" or "Wider Path" within the first 2 crew member unlocks. "Spin Speed," "In Air Correction" and "Speed Wobbles" are acceptable if the first 3 are not available on 1st crew member unlock (otherwise just restart).
3. Highlands - this is the only area you should risk building rep to unlock crew members. For boss ramp, just go around it but watch out for rocks. Difficulty 1/4.
4. Forrest - this area is much easier with wider path or smoother curves. Try and avoid steep races at all costs as it's easy to go off course and hit a tree. For boss ramp, just go around it. Difficulty 3/4.
5. Canyon - this area is similar to highlands but since you're halfway through - I'd urge against building rep to unlock more crew members. For the boss ramp, you do not need to accelerate if starting from the last checkpoint (highly recommend restarting (press circle) from last checkpoint if you are not comfortable with trying on first attempt) but you should bunny hop. If for some reason you don't clear the canyon, land on the side wall and spam circle to restart from last checkpoint - usually, the curves of the wall provide a short moment where you are still and the game will allow you to reset. If the landing area has canyon walls on its sides, you can land on those to soften the fall (again - highly recommend if you are not comfortable with landings, even with landing impact modifier). If you must land on the ground/path, make sure to stay in the middle of the ramp when jumping and keep your front wheel elevated (so that you're landing more on the back wheel and the front wheel is coming down). Difficulty 2/4.
6. Peaks - this area is where you really need to work with brakes and wider path/smoother curves is crucial. Watch out for gap stunts (notified by 2 posts with red markings). Preferably go around them or if not feasible, then go down and up. Make sure you can build enough speed to go up and out of the pit or you'll likely bail. For the boss ramp, you do not need to accelerate if starting from the last checkpoint (highly recommend restarting (press circle) from last checkpoint if you are not comfortable with trying on first attempt) but you should bunny hop and make sure to aim down the middle (both the first ramp and the flying ramp). Your goal is to get on the flying ramp at the beginning of it. If you land in the middle (or farther) - you're better off restarting from the last checkpoint as you likely can't build enough speed to land the last ramp. Again, stay in the middle and you should be ok. If you're nervous on landing and falling over, make sure to brake rather than overcorrect as you're more likely to bail. If you're teetering on the edge, bunny hop to correct yourself. Difficulty 4/4.
7. Bunny hops! If you are attempting this trophy without having completed a bikeout map, then you first learn how to properly use the bunny hop. Remember that the longer you hold down (down analog), the higher you'll jump (up analog). Also, releasing the bunny hop at the middle of the ramp (usually where the skid marks end) will increase the height so be careful when doing that on boss ramps so you don't overshoot the mark (mainly on peaks).
Enjoy