In the current situation I have time on my hands to try things, but only at home (hence the cramped pictures below, with garden toys in). An injury meant last year's trip didn't happen as planned, but I bought the tarp anyway. As I commented before, keeping the bike upright with guy ropes should work, and it does. Here they're attached to the drops. To ...
From the Kryptonitewebsite, looks like both the make and model are open-ended text entry forms. So I think you’d be ok to write something like:
So if you had John Jones make your bike and you’re Carla Carlson then you could say:
Model Year: 2020
If you built the frame yourself, then ...
There are some good answers here, but I don't see my favourite, which is for the stronger rider to set a demonic pace at the front, lashing the other with a constant stream of imprecations and exhortations, turning round with a furious demeanour to bellow "Stay on my wheel!" whenever the partner seems in danger of detaching, or even dropping back ...
FYI I use simple prescription glasses or sunglasses, where the frame is attached to the top of each lens, but not down the sides of the lens nor underneath -- so there isn't a frame at the side of the lens, blocking vision.
Also the arm (between the frame and the ear) isn't thick.
The lenses are long-distance only, not progressive.
The other answers assume your lenses are contaminated by external sources.
A different alternative is that you're the source of the greasiness, from sweat or perhaps hair products or similar. Greasiness implies a biological source to me.
Check your helmet's foam padding, and if its manky then remove it carefully and wash it. You can also try a headband ...
There are cycling helmets with integrated detachable visor. The visor covers the eyes. Yet the helmet is open below.
I see them frequently on my commutes on rainy days. Most are urban style helmets. Ventilation might be a little lacking for very high temps and high exertion.
Here are two arbitrarily chosen examples:
An ex-coworker of mine got a pair of goggles that he could put over his prescription glasses. In his case not so much because of dirt on the lenses, but because wind bothered his eyes.
A lot of the ones you'll find are the high-durability ones for mountain bikers (with thick heavy frames), but it is possible to find lightweight (and not so ugly ones) like ...
I can't think of a way to keep your glasses from getting dirty. It sounds like the dirt could be carried by the air. As you ride the air hits your glasses and gets them messy.
If you get laser surgery so you don't need glasses then all the stuff you clean off your glasses will go straight into your eyes.
You need something to protect your eyes and is easy ...
Time's moved on a lot since this question was originally asked. Now, e-bikes are more affordable (okay still expensive, but better)
A modern ebike with a low assist level can be used to start with, perhaps ramping up the assist level as the ride progresses.
Fast rider can use this as motivation, or perhaps even draught behind the ebike (purely for practice ...