CNN article on plane painting with comments by IACJetlines in good hands with IAC, it seems. Lengthy text article at cnn.com covers the entire painting process.
"
Painting an aircraft usually takes around one to two weeks and the costs can vary greatly. It all depends, of course, on the size of the aircraft and the complexity of the design. For instance, painting a regular passenger plane costs somewhere in the region of $150,000 to $300,000..."
https://www.cnn.com/travel/article/how-to-paint-an-airplane/index.html Has a slide show and videos.
Article is dated 2020 but still worth the read. Techniques not likely to have changed much although costs could well be higher.
Judging by the level of complexity of the graphics some airlines use, Jetlines will be at the lower cost end.