Strongly recommend using some satin varnish over that to protect it. If you don't, it comes off after a few washes. Got pretty good results on mine by doing the chrome pen and then immediately using Humbrol satin varnish over the top. The chrome goes more silver than chrome when you do this, without going milky, and it looks a lot closer to the factory finish. It also survives washes far better.
Those Molotow pens are pretty amazing, they've been such a time saver with little projects, they're one of the most convincing chrome pens out there. I've even used one to dot in rust spots on some old chrome hubcaps (non-BX stuff) which worked way better than I expected it to.