On reading again it appears you are all talking about filling a 25 L vessel ?
So yes filling a bucket with resin and pouring it in may be fannying about

definately fill with some water though before trying to re insert the riser tube.

I have an 11 L vessel
I found that using a scoop or funnel was messy and slow. Resin is light and sticky, the funnel would get blocked, resin would get spilled and stick all over the thread of the vessels opening.
I found that it was less messy, easier and half the time for me to fill my window cleaning bucket with resin to 10 L mark and add water ( just enough to be fluid ) and pour it in to the vessel with no mess or spillage.
But doing this with a 25 L would be perhaps more time consuming as it would take several buckets
