Hi chaps, I have some sci-fi tanks that I've just painted up and they look great but as they're quite sleek and simple they are just missing something so I was going to put a symbol on the side of the tanks (in this case a logo of sorts) however I could never free hand it so what is the best way to do this? Would printing them off on paper then pva them on work (I would give them a couple of layers of varnish on top as well)?
If you have a decent inkjet printer, doing your own decals using decal sheet and gloss varnish is a simple enough process, although you would obviously need to design the symbols in high-enough resolution for it to look good.
Also, an inkjet printer cannot do whites; the best results would possibly blacks or dark tones, while lighter colours (reds, yellows in particular) would only work decently well on a light paintjob.
Apart from that, the "printing on high-quality smooth paper and glueing on" does work, but you should try to make the piece of paper conform to an existing panel shape, or have it resemble a panel or hatch so that the thickness doesn't look too out of place.
A final option which I regularly use would be a stencil. You could print numerals or geometric designs on a medium-strength paper/cardboard (160g/sqm), then cut those out using a scalpel or very fine modelling knife. After that, place the template on the spot where the design should go and use a stippling brush or sponge to apply some layers in a drybrushing fashion.