sanding guide coat

[lt1chevelle]

what grit do u suggest sanding guide coat (https://www.pro-touring.com/forum/showthread.php?t=53529), 120? and is it best to do it wet or dry?

[Paint God]

It depends on what is under the guide coat and what you are doing once it is sanded.

Is the guide coat over

Paint?
Filler?
Sealer?
Spray Polyester (like G2 Feather-fill)?
Water-based primer?
2K Urethane primer?
Lacquer Primer?
Bare metal?

Once you sand it are you

Priming it?
Sealing it?
Painting it?


If you tell me what you are trying to accomplish I will advise you.

[lt1chevelle]

it is over G2 Feather-fill, i will most likely seal it once its sanded and fix spots that need to be fixed and just spot prime them and then seal the whole car. is it ok for it to sit sanded till i can get around to sealing the car ?

[manicmechanic]

I would start with 600 grit, 120 is way too rough if your going to make this the final sand before seal and paint. After the once over with the 600 you might also go over it again in 800 depending on how smooth you want it. I like to sand my seal coat as well and use sealer that allows for that. I don't see any reason that you can't let it sit before sealing it, but once you start with the sealer you better be ready to paint it too.

[JRouche]

it is over G2 Feather-fill, i will most likely seal it once its sanded and fix spots that need to be fixed and just spot prime them and then seal the whole car. is it ok for it to sit sanded till i can get around to sealing the car ?

You are sanding the filler right, not the guide coat, its just a marker. 600?? Ummm no! Wont even remove the filler like you should be doing.
You are using a guide coat to see the removal of the filler, or high build primer in some cases, most cases.

180 grit if you are sanding filler or high build.

Paint god asked the right Q. What are you sanding. Its not the guide coat, its what is under it, thats what you are sanding. JR

[Paint God]

G2 Featherfill! Ouch! Im sorry. Your going to build some arm muscles on this one. Ok. This is going to start all kinds of controversy because my technique is going to sound harsh, but I promise it will get your car the straightest and save you a whole bunch of work. I use a spray polyester made by Spies Hecker that sands really nice. G2 featherfill is also a spray polyester but is hard as a rock. I used G2 ONCE with success. It was just a lot of hard sanding.

I recommend that you use some really coarse sand paper to start with and then move down. There are two reasons.


The coarser the paper the flatter it will cut, so the straighter your car will be.
The coarser the paper the easier to sand.


Talking to amateurs and hobbyists the biggest mistake I see them make when it comes to sanding is they use to fine of sand paper. What happens is if you use to fine of sand paper it wont actually cut the surface flat (even with a block, but I will get to that). It will just smooth everything out leaving the waves to some degree.

The type of blocks you use makes all of the difference in the world also. The most popular block out there right now is the the Durablock. These are nice because you can bend them on curves. The problem with them is that you can bend them so you need to be an absolute artist to make a flat panel straight with them. I recommend a long durablock on the quarter panels of any Camaro because they are curved. The rest of the car should be blocked with a rigid "old school" wood long board. I use the Hutchins wood long board made for "stick it" paper. Autobodytoolmart.com sells all these blocks.

Now for the sand paper. I would start with 80 grit. Yes you read that right. You can buy 3M 80 grit long board stick it continuous paper from and supplier. It is a roll that is the same width as your block so you can cut it to fit any block. Just block it out removing the guide coat.

Once you have that finished I am sure that you will have little things to fix. Go ahead and skim 3M "Easy Sand" polyester filler right over your G2. Since they are both polyester based it will work find. Finish this work out in 150 grit.

Now your have a decision to make at this point. After blocking in 80 grit is there still lots of G2 left? If you broke through everywhere and it is pretty thing then you might want to throw another 2-3 coats of G2 on it. If this is the case let it shrink for a week and repeat exactly what I just instructed in 80 and then fix any small things in 150.

Once you have this finished and you still have plenty of G2 left on it go ahead and guide coat it again and block the whole car in 150 grit. You can buy the same sand paper as I mentioned earlier in 150 grit.

Now I hope you know that you cant paint over G2. It is porous like Bondo so you need to seal it. I would recommend sealing it with a high build 2k urethane primer. spray 3-4 coats of that on there and let it shrink for a week. Guide coat and block in 220. You can buy 220 in the same roll i mentioned earlier for your long board.

The same thing applies here. If you are satisfied and there is plenty of material left just go ahead and guid coat it again and wetsand with 400 or 600 grit (depends on the type of paint and color).

If you have any problems or questions dont hesitate to send me a PM. +