You can use Float's Quick Budget Edit tool to easily copy and paste your forecast from elsewhere (including a spreadsheet) into Float. You could also use this to copy budgets from one scenario to another. While you can't upload direct from a spreadsheet, you can certainly copy your budgets right in.
You can also use Quick Budget Edit to move easily between cells and enter your budgets more quickly. And you can drag a cell to the right to copy it forward.
Here's how it works: