Not going to go into naming names or anything, but this being in the air some 15' or 20' is what makes this a little hairy for the OP. With or without experience, I hope he has the correct insurance for himself and liability... should he drop something on someone's head. That's my first concern.
Next, again.... being that high makes a pounce almost out of the question. I didn't even think to mention that originally because it goes without saying. However, having so many novices when it comes to hand painting, I forget sometimes.
Before doing anything, you must first prep the wall if needed. Personally, using a grid was always something I used when doing pictorials and/or large areas.... not this kinda layout. This being about 5' x 65'... I'd be on a 17' walk plank between two tall ladders. I would draw in a top line and bottom line. Sketch in with the charcoal all the letters I could fit in the first 15 or so feet. Probably about three, maybe four letters. Cut them in, fill them in and then do the shadow right away. Move to the next section and so on til finished.
If this was near ground level, I'd again put both top and bottom lines and charcoal in the letters from start to finish, cut them in, roll them in and come back and cut the shadow in when finished with the first color.
As for being the same skill level as painting your house, please don't say such things unless you're lettering your house while painting it. Has nothing to do with experience or talent. Has everything to do with paletting your paint, right consistency and proper prep work. None of which is done the same as in house painting. Ever wonder why some wall lettering jobs have lasted 30, 40 and 60 years, while most house painters jobs might last 5 years before needing a re-paint ??
No, the two shouldn't be compared to each other, but if that's all you think of it, then its no wonder we have some of the problems in communications and understanding of hand-painting techniques.
Actually, it even takes a house painter longer to learn how to properly paint and they too would probably feel a little insulted, that you hold no respect for what they do either. Truthfully admitting that you could learn on the job and not screw it up too bad is not something ANYONE's customer would like to hear. I would never place that fear into a customer. Things go bad, and jobs go south for many reasons, but they shouldn't be actions of negligence of not knowing your trade and treating it so lightly.
Sorry, but this is the kind of attitude that just give me pains in my stomach sometimes. Sorry to vent on ya, but it had to be said. I'm sure you meant well, but it didn't come across that way at all. If you understood, thank you.... if you took offense, then I'm glad I said it.
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