Cut the trim
I suggest making your own trim by ripping it out of less expensive non plywood or OSB backed composite hardboard siding. Buy solid sheets without grooves if possible to minimize waste.
Otherwise just cut around the grooves in normal siding. No groove siding is siding without the normal grooves in it. You could use regular grooved siding but then you will have no control over where the grooves fall on your cuts. Or else you will have a lot of waste if you try to plan your cuts around the existing grooves in the normal siding.
The no groove siding doesn’t need to closely match the main siding. It just needs to match the texture so that it looks good when painted. If necessary you can buy one brand of grooved siding and another brand of no groove siding.
You will definitely need a table saw for this job.
Most of the trim will be 2 1/2 inches wide. Use this for the corners and around the doors and the windows.
The trim inside the garage door frame will be deep enough to cover the framing. The trim around the roof edges will be wide enough to cover the 2×4 frame. A little wider or narrower to fit your taste.
Pass door and window
Install the pass door and window per the manufacturers recommendation. Then trim them beginning with the side pieces cut to the length of the opening. Then cut the top and bottom pieces to fit. Feel free to caulk under the top piece of trim.
Overhead door backing
Install 2×6 framing at the back of the overhead door opening for the track to attach to. The 2 side pieces should extend 12 inches above the top of the door opening. Just run it up to the base of the trusses. Then fill in along the top of the from side to side. In the very center you will need another piece running up to the base of the trusses for the garage door opener to attach to.
Trim overhead door
Trim should cover the inside of the framing including the door backing. Then trim the front of the opening with 2 1/2 inch trim.
Fascia
I ike to cut my fascia a little wider then the 2×4 framing. Like 5 to 6 inches wide. Cut a test piece and put in place to help make your decision. Begin at the peak and install them down to the truss end boards. Then install them on the truss end boards.
This is your last opportunity to adjust and correct any imperfections in the roof line.
Bird boards
If you are not going to cover the soffits then you will want to install bird boards between the trusses. Cut holes in them to match the holes in the truss blocking if necessary.
Cover the soffits
If you want to cover the soffits you will need to install some 2×4 blocking on the gable end rafter to nail it to. Then cut strips of no groove siding and nail it in place. The trim on the eaves will be nailed to the trusses so it will not need any additional blocking.
You can buy vents to install in the eaves if you like.
Install a piece of trim around the bottom of this soffit cover.
Corner trim
Trim the corners with 2 1/2 inch trim. You might need a short splice to make it reach up to the underside of the roof of the bottom of the soffit siding.
Drip edge
If you want the drip edge painted then install it now. If you want it left in its original color then wait till after painting to install it. I prefer it painted so it doesn’t distract from the roof line.
Caulk
Use a good quality caulk and fill in any nail heads through the siding. Caulk the grooves of the siding. Calk around the trim, particularly at the top of the doors and windows. Use the caulk to fill in around the bird boards and to fill any gaps where the trusses meet the end board if they will be visible.
Mask
Mask the door and window and the concrete around the overhead door opening and at the base of the pass door. Mask anything else in the area that you don’t want to get over spray on.
Main color
A sprayer is almost a requirement if you leave your soffit open because it will take too much time to paint everything with a brush. You can rent a professional quality airless sprayer from Lowes or Home Depot.
I like to spray the first coat or 2 and go over any tough areas with a roller.
Then go around with a brush and paint over any nail heads that didn’t get covered earlier. Recaulk them if necessary.
Trim color
Paint the trim color with a small roller and brush. I like to paint around the doors and windows, the corners and the fascia.
Install garage door
I never install my own garage doors. The store I purchase it from usually has their own installation team. It’s fairly cheap and they know what they are doing. And they warranty their work. There are lots of little parts in a garage door track.