How to alternate Tylenol and ibuprofen in toddler

My LO is 18 months and cutting molars. He is absolutely miserable and my household is getting over a cold so he is also congested. He won’t sleep more than 20 mins most of the night and he is really unsettled. He cries all day unless I’m holding him. Barely wants to eat. I talked to his doctors nurse because he had a little temp spike (low fever - 100.4) and she said I could alternate Tylenol and ibuprofen for him for his teething pain. I was like ok and was talking about other things and forgot to ask how to do that. Does that mean I can give Tylenol then two hours later give ibuprofen? Then two hours after that Tylenol again? I’ve only been doing Tylenol every 4 hours and it helps but he is still miserable all day and night. I would call back but they’re closed for the holiday weekend.