Reliable guy or not, he was right: if you're unsure about which future tense to use, 'be going to + V' really is your best bet. This is because you can use the 'going to' future in more situations than any other future form.
Here are three examples:
- When you've just made a decision, you can say, for example, either "Don't worry, I'm going to help you" or "Don't worry, I'll help you" (but not the present continuous future)
-When you're talking about plans you've already made, you can say "I'm going to visit Grandma tomorrow" or "I'm visiting Grandma tomorrrow" (but not the 'will' future)
- When you're talking about fixed arrangements/scheduled events, you can say "I'm going to fly to Paris tomorrow", "I'm flying to Paris tomorrow" or "I fly to Paris tomorrow" (but not the 'will' future)
As you can see, it all depends on the degree to which the future event is decided. Also, as you can see, 'going to' is an extremely flexible form which can be used in many situations where the other future forms would be wrong.
It's also worth noting that 'will+V', which many non-native speakers wrongly assume is the 'real' (standard, normal, or, as you say, 'neutral' future in English) is actually far LESS useful than other future forms. Most of the time, when English learners use 'will' to refer to the future, it's unnatural or - as in the cases above - simply wrong.