Start by removing the existing coat of sealant and stain. It may be literally impossible to completely remove the old sealant glaze. However, you should remove as much as you possibly can by sanding the wood surface with fine-grit sandpaper. Removing most of the existing stain and sealant will make your work easier and you will be able to make the new stain coat very even.
Making the stain choice comes next. Bear in mind that you will never be able to stain an already stained wooden surface and make it lighter at the same time. This is why you will have to choose a stain shade which is the same or slightly darker than the existing stain.
Once you have chosen the stain shade, use foam or cloth brush to apply a generously heavy coat of stain on the wooden surface. Make sure that foam or cloth brush strokes are in the same direction as the grain of the wood.
Read manufacturer’s instructions to check how much time the stain will require to sit and soak into the wooden surface. Wait for the appropriate amount of time. Generally, almost all stain brands require approximately 3 to 5 minutes to completely sit and soak into the wooden surface.
You now need to remove excess stain from the surface that you are re-staining. Use a clean cotton cloth for this purpose. If you are working on a relatively large wooden surface, try to work in small sections. This will help you wipe off excess gel stain in time before it dries too much.
The shade of the surface may not be what you are looking for. If that is the case, simply apply another coat of gel stain, wait for it to set in and then wipe clean the excess stain as you did before. However, it is important that you let one coat of gel stain dry completely before applying the second one.