With last season's star-striker Brett Pitman still nursing a knock, ex-Millwall forward Grabban partnered Wes Thomas in attack and opened the scoring with a header after 26 minutes before rifling in the winner from 25 yards in the 66th.
Promotion-winning boss Howe said: "I am really pleased for him. Every striker needs to score and he took his goals really well.
"He maybe didn't grab the headlines last year but he was a key part of the team. He has always performed well even when he perhaps didn't score the goals.
"He scored two strange goals for him here - they are not his trademark, a header and long-range shot but I thought him and Wes were a real threat.
"I am happy with Brett, Lewis and Wes but really that is all we have for recognised strikers and to just have the three is not enough.
"We are looking but won't be rushed and panic while these boys are fit. They deserve their chance and they will get it.
"It was an important game for us as we knew we needed to start well. We scored two goals and were somewhere near our best today but we are going to need to do it every week."