Upvote:2
You might be lucky and persuade your airline to check the bag through onto the separate ticket. But I wouldn't count on it, and even then it's bound to get lost on the way.
If you cannot arrange that, you will have to pass through Schengen passport control twice at Brussels. The route that goes landside is often congested for non-EU passport holders, last time I went there with an American colleague she was stuck in the queue for over 90 minutes in both directions while I, for the time being an EU passport holder, sailed through in under a minute. After passports you'll need to collect your bag, clear customs (which is usually a non-event), go to the check in counter, drop your bag, go through passport control again, re-clear security, go to your gate.
At Brussels you need to be careful not to go outside the terminal from arrivals because there is a one way system hastily imposed after the airport bombing that is very confusing and enforced by armed police. Getting back inside again is not signposted at all. I think the quickest way is to walk all the way to the parking garage (to your left) and take the lift to the top floor and cross the road (which is empty of traffic now). However inside you can just go up the lift. So avoid the cigarette break until you find the departures floor.
Upvote:5
What will be the procedure?
How much time will I need to do this?
Impossible to know up front. You may be able to do this in an hour and a half or it may take 4 or 5 hours depending on unpredictable factors. No connection is ever guaranteed so it comes down to risk management: On a two ticket itinerary you carry the full risk of a missed connection yourself.
Personally, I use a minimum of 4 hours for a two ticket connection and in this case, I'd up it 5 or 6 hours, since Brussels immigration and security can be real time sinks.