No!!! You cannot add ammonia when you have fish in. You'd just poison your fish.
If you don't add a full complement of fish after the cycling is finished, you will need to allow some time for the biofilter to catch up after each additions thereafter. Exactly like it happens in any ESTABLISHED tank.
However, unless the initial load is ridiculously low (as in the beginning of regular ("fishful") cyclings), such mini-cyclings are short and not prominent. Think of it this way: if bacteria doubles in 24 hours, and you have a million of them, you'll may get two million tomorrow. However, if you start with 10 bacteria, you may only have 20 a day after. An initial capital so to speak. So, if you start with 30 fish, you may add 3-5 of new ones every week of so thereafter. If you start with two fish and allow the major part of the filter to die off (which doesn't happen overnight, by the way), don't expect to double their number weekly without seeing noticable picks of the wastes.