You can do allsorts of nice paint jobs using spray cans your imagination is the limit, the tricky bit is not hammering onto much paint so you cant see the rest of the design and obviously shadows would be a touch tricky
.
I used to measure the size of the area i was painting, draw the design out on card and cut out as a stencils, laydown some wide masking tape (ovelap if neede be) on a cutting board, draw around the stencil.
but it is also more costly to buy loads of cans at £5 ish per can, I would normally do 3 colour max with cans. 2 main colours and a dividing colour.
Good luck