If you are confident that you can properly follow the manufacturers instructions; you can do it.

 

As long as you do the prep right the epoxy will adhere well. How well you apply the epoxy will determine how well it looks.

 

I worry is all I've got is a 1800 PSI home pressure washer which won't really clean the floor well enough.

 

Your pressure washer along with a good degreaser detergent and scrubbing [I like to use an old broom] might be enough ..... but we've not seen your concrete.

 

Any project that requires tools I will never use again, or a project that I will never repeat to gain eco-to-scale, I will usually outsource. Have you obtained a quote? if so, what is the cost vs DIY expenses...If it only cost $12 more for a cold six-pack to sit down and watch the contractor, you could have your answer...also, if you are married, do you have a wife that will point out all your errors for the next X yrs?