my bonsai is going to be overwatered soon because the fertiliser im using at the moment needs to be dioluted with water once a week when the soil is still damp or wet! i need a way to feed my bonsai without overwatering it!

It depends on the soil and type of tree you are fertilizing. Yes you most definitely want to water the soil first, however, adding the fertilizer once watered shouldn't technically cause you to overwater your tree.

I would revaluate the type of soil you are using if you are concerned. I think we all fertilize once a week or every other week and I haven't had issues with overwatering. Also, depending on your location, you may want to cut back on fertilizing this late in the year.

What country are you in? At this time of year in the northern hemisphere the trees are slowing down and fertiliser is reduced or stopped.
You cannot overwater, only water too often as I was told.
If the tree is not in need of being watered then dont it is as simple as that. It is not necessary to add fertiliser to a strict schedule. And you should not be watering to a schedule either. Water when needed.

yes water when needed...water wait a few hours water with fert. spring is the time for weekly fert.,in fall I put a slow release fert and stop water fertilizing. fertilizing too late In the season on young trees will cause them to put out new growth when they should be storing energy which will leave you with a dead tree next spring