oil tank trouble

The seller of my bike has made a big mistake: Hes has sandblasted the tank without proper sealing !! So there are a few sandcorns in the tank, and i can't get it out. So what are you doing? Should i use a gas tank sealer/rust preventer ? Cleaning with a vacuum cleaner and flushing was not very successfull !
The tank is new powder coated...

Thanks for any good idea
Marco

Take it to a radiator repair shop, they will have a large powerful washing tank which will work wonders and the powder coating should be unaffected.

I had a similar problem, I flushed and rinsed the tank many times with a degreaser eg Gunk. Then I got a piece of clean rag wrapped round a screwdriver and coated it in grease, then swabbed out the tank through the oil feed opening, picking up grains of sand and grit with the grease.
A full evening of rinsing and swabbing got it clean.

Kommandos idea is the best though.

Which ever you do just make sure you get rid of it ALL !!!!

Thanks for your inputs!

Marco