After 40+ years its anybody's guess what state the glow system is in.. they are frequently modified, sounds like you have a new push button for glow - the glow indicator may or may not work, if it does work it can take up to 10-15seconds before it actually indicates and even then you'll have to squint to see the very faint glow that it'll show - its not a bulb, but an actual heated element that glows behind a small mesh screen..
Starting procedure will depend on what's been done to the glow system - maybe its got the wrong plugs, maybe its got the right plugs... its anybody's guess.
In general expect to have to glow for at least 10 seconds, then start with full throttle, coming off the throttle as soon as the engine starts of course. Reassess glow time based on your experience - try it and keep as short as you can get away with. The glow time required will depend on the current temperature and will be totally unnecessary when the engine is warm.