One strategy that made artillery very usefull in colonization was having only 1 coastal city. All the king his landing forces would attack that city, inland cities would only require a few troops. This coastal city can then be supplied with artillery produced in inland artillery colonies(colonies who produce a lot of hammers and a small amount of tools), even cash crop cololonies who produce hammers(like quite all my colonies did) can eventually produce artillery after they have build all the rest they need.
Producing artillery, producing horses/muskets, buying units with cash good profits, buying troops with aztec/inca conquest profit or any mix of them can all be good and effective strategies in colonization. That was exactly one of the things I loved so much about colonization: There where many roads to victory in the original colonization.