How to edit the fin number on GIMP?

[Yebiz]

Hello, I'm trying to edit the fin number of an aircraft (for personal use). I've done it multiple times, but this time there are screws behind the letter. They remain apparent and the letter is semi-transparent. Here is the problem, I have no idea how to do the same on GIMP (I don't own PS). I have tried setting the layer's opacity to 50 and colouring it but I can't find the right color and the screw is hard to notice... Can someone guide me through this? I'm sure it's not so hard to do but I have tried quite a few things and I can't find any tutorial about it.

Thank you (pic attached to explain a bit more)

 

[Atarium]

Hey! Don´t worry. GIMP is like Photoshop for  painting if you know how to use it
 

1. Import the fuselage file to your gimp.

2. Mark a part of  the red color with a box or manually. 

3. Copy that part.

4. Paste it and cover the old Registration as long as you can´t see the registration anymore.

5. Then just insert your Registration!

If you just want to change the "C" to a "G".

1. Mark the color of the "C" with the pipette.

2. Mark the "C" to a "G" 

3. Fill in the marked "Box" with the color you took from the "C". 

[Yebiz]

Hi, thank you for answering! However I think you misunderstood (and I forgot to add that I know how to replace letters). What I'm looking to do is to replace the letter like if it was painted over the screws. I want to see the screws behind the letter, I tried by changing the opacity to 50 an less, but the results were not that great (see screen above). I'm wondering if there is a technique that create the "painting over but still see through" effect? 

Here is what I did in between: 

Thank you again

Edited March 4, 2019 by Yebiz

[Atarium]

You are talking about layer multiplication. 

That could be quite taff here.  The only way to do this is to paint that part by yourself. 

Copy the white paintkit and lay it over the norwegian paint. Then cut everything except the Gear doors so that they are white now.

Create a new layer with options "Multiplicate".

Then paint the Nose Gear Doors red like on the original. It will take time to find the right color due to the multiplication.

Then add your registration - set the layer option to "multiplicate" too. 

This would be the same progress like a normal paintjob...

[Yebiz]

Thank you for helping. I found an easier way by asking on reddit. u/Grue wrote this: Duplicate the red background, use Color to Alpha to remove the red (use color picker to select the exact shade), then use this layer (which now should be transparent except for the screws) to apply screws on letters.

It worked but the contrast was too low. I added a luminosity mask to counter that and boom, like a true paintjob!

Thank your for taking time to answer

[Atarium]

Cool!