You didn't say what level of "restoration" work you are embarked on, but the strip level suggests a complete going through.
If you are at the stage where the frame is stripped then the detail level demands a professional paint/powder coating which ever floats your boat. You are headed down a road that is paved with $100 bills, cheap out at this stage and you migjht as well pitch 15-20 of those bills down the shitter. The value of the finished motorcycle will be judged, largely, by the level of consistency you applied to all components and their assembly.
That said, and if you are just trying toi get a two wheel vehicle to a rideable stage, that just hgappens to be a Norton motorcycle, then paint everything with spray cans, why stop at the frame the tank, side covers and fenders beg a coat; just make sure that the steering head and axels are tight and that the brakes work and you won''t get hurt riding.
I'll acknowledge that *some* spary can paint jobs can be decent, just make sure that all your paint comes from the same lot; there are shades of black.
I am not trying to rain on your parade; you will be spending between $5K and $10K, at a minumum with modest engine/transmission and suspension work, what's an extra $500 to $750 for a properly prepped and painted frame/engine cradle/battery tray/coil mount/other small bits?
The allure of a motorcycle is also it's bane