What Gelcoated Cars have you worked on????there arent too many cars out there with Gelcoat on them....99% of them are Painted over the gel in Auto applications so it is Very Likely that what you thought was Gelcoat was actualy clearcoat thus the reacting identical to clear was because well it was clear or some other form of urethane topcoat....
on to the Gelcoat....this was cut and pasted from a previous post i made on how to properly polish gelcoat so it may not al apply to you...I did edit it but quickly...LOL...
Gel coat is a totally different animal then paint......it is porus so it sucks up product like crazy.. when oxidized like that any and alll automotive products are a waste of time and money....and conventional ways of detailing go out the window.....
Clay-dont bother....any contaminants that stick to oxidized gel will be gone when the compounding phase begins and unlike automotive paint the compound used is very coarse so small bonded contaminants are nothing to worry about.....
wet sanding Gelcoat is not advised unless you have intimate knowledge and tons of experience with gel...
you need to hit the local marine supply store and get the products below.....
Knights Spray9....this a i a HD cleaner that is used in the marine world....dilute it in a 5 gal pail at about 1/4gal to the rest of a 5 gal pail of water and wash the boat well with it....do small sections at a time rinsing well in between....you may notice it yellowing the badly oxidized spots but thats OK it will disappear when it dries....
once its thoughroughly washed get out the WOOOL pads....3m superbuff 2+2 is my pad of choice on a superbuff adapter since they
flex alot more than a velcro backed wool pad and allow you to apply more pressure to compound without causing uneccesarry marring.....keep plenty of fresh pads handy (pad is double sided so i would say 2 or 3 for most jobs) since once they gum up they need to be let sit to dry out then spurrred.....Spurring a wet gel compound pad usually doesnt work as well as a dry one....
for COMPOUND use
Meguiars #49 compound....this compound is very aggressive and has a diminishing abrasive that lightens up as you go as well as essential oils that the gel needs to allow for proper compounding....start in a small area and spread at slow speed....once evenly spread out run higher speed than you normally would on paint and apply decent pressure....just be cautious in the decal areas as they dont like the pressure....with gelcoat speed IS your friend so dont be afraid to spin the wheel to 2200-2500 RPM......work the area until the polish is cutting less and then drop down to slower speed and allow it to basically dry out.....then wipe the panel with a towel to remove any light residue
after you have compounded the entire thing then its off to POLISH.....now you can use automotive polishes at this point with some success if you have done the Compound step properly.....you can experiment with whatever polishes you have in your arsenal.....i happen to like
Menzerna SIP for this step as well as 3M Finesse it.....again dont bother with Foam pads stick to a wool blend or synthetic polishing pad such as the 3m yellow and use the double sided pads on the superbuff adapter as mentioned earlier....this step will take some time to get the swirls out (roughly twice the time of paint) and you will probably have to polish twice in order to get it looking nice....
after this step its back to the marine products for some
Meguiars #45 Boat/RV Polish....apply this by hand or machine with a foam pad on slow speed and work it well....remove before it dries.....again using a terry towel.....
then my wax of choice is
Meguiars #50 cleaner wax....i know its a cleaner but it works well and lays the foundation for whatever you choose to top it off with....be sure to apply the wax generously and allow it to dry fully and then buff off with a terry towel....(microfiber is not your friend on gelcoat)....i usually do 2 coats to be sure i fully covered the whole thing as its easy to miss a spot on things this large.....
keep in mind as well that with gelcoat the word Correction is basically non existent....gel will always show some swirls here and there and especially if allowed to sit outside in the sun it will fade and show swirls that werent there when you finished as that is the nature of the beast.......
hope this helps......