I think I posted in your other thread. What about instead of spraying clear. Why don't you just put some clear 3m vinyl on the top tube instead?
uj/ Not gonna lie, I use this 3M Paint Protection Film on my watch bracelets.
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I put it on the clasps since that's the part I always end up fucking up. You can't even tell it's on there from anything more than "bad breath distance."
https://www.amazon.com/dp/B01LY0GIZV/ref=cm_sw_r_cp_apa_glt_fabc_FM4B6VRX1171KB689AS3
This stuff is amazing and a while lot cheaper, and not that difficult to install. I did it to my bike back in December.
YouTube installations videos to get comfortable
There are companies that make kits of laser cut helicopter tape for specific frames, which I'm sure work great, but personally I think they're too expensive. I've had good success with this the 3M tape from this seller. Let's me cut tape to the shape I need and it's nearly invisible once installed.
This is what I got recently! I used soapy water to apply so I didn’t have to get it perfect the first time. I was able to work out most of the bubbles that way. link
It goes directly on the frame and protects it from the cable rubbing the paint off. The paint job is... ok at best. It comes off very easily. If you put any protective tape on, just know taking it back off may pull the paint with it. I had a small issue just with the smaller ones you get in the box. I used this based on a recommendation from another Reddit thread:
Try PPF, you can pick up a roll from amazon pretty cheap.
We put it on our door sill, not sure how it'd work on the plastic parts.
I can measure it out later today, but this is the one I wrapped my other Mash in - https://www.amazon.com/gp/product/B01LY0GIZV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
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It covers the entire bottom half of the down tube that's exposed to the ground/grime/water/dust/rocks, which should be sufficient. It's more than enough to wrap around the entire chain stay and seat tube.