start sometime around 26 weeks
remember that milk is still the primary source of food and nutrition for the first year, so don;t worry about getting baby onto 3 meals a day too quickly
iron stores only start to deplete at 6 months, they don;t run out , so don;t be scared into starting baby onto solids earlier to rebuild iron levels.
don't put anything in the bottle to help them sleep through
try BLW if you are stressing, as it is , in my opinion , the far easier way to wean, as you are not having to cook and blend special food, you simply offer finger foods, or bits off your plate.. and don;t worry if baby does not eat lots, it is about exploring taste, texture and food itself
if you go the puree route, remember it is just tastes at first , not full meals, so don;t worry if baby eats a little
there is not a window of opportunity you can miss if you don;t wean at 4/5/or even 6 months.. some babies do better if they start later, don;t be surprised if your little one can go days without eating more than a bite or two at first
as long as having lots of milk, doing wees and poos, happy and alert, you are not going far wrong
and on the whole, solids won;t suddenly make your baby sleep through if they haven;t been doing so