I really don’t know if what I do is right, but it seems to go ok for me - everyone is different I guess.
My general rule is that for a mid week training session under 2 hours I only have water, I also don’t have anything before hand (never have). If its a particularly hard session I’ll try to have some sort of recovery thing straight after - I switched to Infinit about a year ago and I use their Repair stuff for this.
Long ride of say 3-5 hours I’ll use Infinit Go Far plus a Clif bar, and long runs I use SiS gels every 30min. I usually do long runs after lunch so I’m not completely empty. So basically I practice what i’ll do for race day during the long ride & run.
Again, I’m not an expert on this - but I have noticed that over the years my consumption of calories has come down compared to the banquets I used to think were necessary.