Yes, be sure to shake the dye thoroughly before and after mixing. Always mix enough dye to complete the job.
Use Colron Refined Interior Lacquer. Clear waxes can be used over the top of Colron Refined Wood Dye to give a coloured wax effect.
No, the pigments in the wood dyes will fade very quickly outside.
Wood Dye penetrates the wood and so sanding is the only way to remove it from the surface.
As long as the colours are from the same product range they can be intermixed to make bespoke finishes. Always make sure you have enough product to complete the job.
The filler will take a wood dye to some extent however not the same extent as the surrounding wood. A wood filler closest to the intended finish is a something to consider.