I had to think about cling film, but my imagination says it will not be even, even if you dont stretch it tight its going to be tight on the corners and be really thin or non existent

If you have not seen it look for topics here that use off the shelf 3% liquid, I did it to my very badly yellow apple //c and while not perfect (it could go for another run) I am very pleased with the results

I like to state that I made nearly 10 gallons of the stuff for less than 7 bucks with a trip to the "dollar tree", and still have almost a half lb of oxy boost

it just takes more time and light

as far as the insides, yea liquid might cause bubbling of the RF shield paint , when I do my SE I am thinking about doing a thin coat of spay on "plasti-dip", if you dont get it on too thick or let it set too long it peels off, although I have not tested it