Help!! In need masking techniques!!

I have been modeling once in a while (mostly weekends). My most troubling modeling problem or hindrance is MASKING. MASKING FUSELAGES to create demarkation mark for belly and top surface of ACs are bearable but MASKING CANOPIES that big pain in my modeling especially those with curved frames such as Mig-17, 19, 21and others............ We dont have pre-cut masks here in the Philippines and therefore have to use either draftman's tape or tamiya masking tape. There's got to be an easier way!!! Any help. information, or tips are most welcome.