+1 for the Camco Tri-Levelers.
I also carry a couple of screwed-2-high 2x8's and three or four single 2x8. You can use a single 2x8 on top of a Camco Tri-Leveler to create an infinetly variable ramp, and for extra height. I usually only use the 2x8 units. Unless, I need a lot of height or I want a ramp instead of a block. The wood pieces are stored outside, in the wheel well area, so cleanliness is less important. The pair of Tri-Levelers go in a plastic bag on the back seat, so I try to keep them clean. Their matrix of plastic will pick up an occasional pebble, but it's easy to dislodge them. Cleaning is easy because the plastic doesn't absorb water. They're a little heavy and bulky, but I like 'em.
The trailer gets 2x6 blocks. Enough to get the motorcycles out the ramp door.
I don't go Ape-poo about level, but after 25 years of carpentry, I can step back, look at it, make my block selection and get pretty level. Certainly between the lines, but, often, dead on. I carry my 2' level I use for hanging cabinets to check my eye, just for fun. Comfort isn't my main concern with level. Reading about a refrigerator's slow demise, from whatever it is that settles in the wrong places because they're un-level, gets my attention.