Plunge router or fixed base?
OP said he was doing a T-Track profile, so... If blind (fixed start and/or finshed, away from an edge), then I drill a hole with a forstner bit (just slight bigger than the diameter of the t-slot bit) at where the t-bolt will drop down into the profile. Start the slot with a straight bit or spiral bit, in steps, about 1/4" depth of cuts. Then the T-Slot bit.
"Don't worry, I saw this work in a cartoon once."
"Usually learning skills and tooling involves a progression of logical steps."