after finishing printing ,can I use it right away,or do I have spray something on it?

Depends what type of printer was used. If it was printed with an inkjet then yes it needs to be sealed before using. I just use a light coat of an acrylic glosses spray on my printed decals.

If a laser printer was used then sealing is less critical because laser printed things won't run when wet, as they are essentially melted plastic rather than ink.

will tamiya flat clear or clear acyrilic work?

Yes, Tamiya will work... I printed mine with an inkjet printer then I sprayed them with Tamiya clear coat from a spray can and that worked just fine.

Hisham

All,
If you really want the ink to stick to the sheet, clear coat your decal paper with clear flat first, BEFORE printing. Let them dry for an hour after printing, then clear coat with either flat, semi-gloss or gloss to suit your needs. Even better, use
Micro-scale decal solution to coat the decals to ensure they remain flexible. This method ensures that the ink is trapped between coats of sealant. Otherwise your decals may be sitting on slick decal paper with a only a coat of sealant on top, but nothing to keep water from seeping under the edges and dissolving the ink. I've been making custom decals for years with the method above.
VR Russ