Well, it is the best way I know! Add to that the fact that when you brush a paint on, it is rarely absolutely identical to when you spray it. For Luftwaffe WW2 aircraft, that is not always a problem, as some aircraft, especially Messerschmitts, tended to be fitted with canopies which were painted before being installed, and so did not duplicate the camouflage pattern.
When the kit is nicely engraved, masking with a bit of Sellotape and running a pointed scalpel along the engraved lines is normally not too challenging, although sometimes, you really do get fed up with it! Maskol, a rubber-based masking solution, can also help. When you remove the Maskol, though, sometimes it slips out from under the paint, and leaves paint behind where you do not want it to be. This can be easily removed with a bit of sticky tape.
Do not however leave the masks in place too long, as once the paint has hardened, as opposed to dried, it'll tend to crack and chip along the edges of the tape. Equally, do not varnish over masks you have painted on already, unless you do it soon after painting, and remove the masks quickly enough.