Maps from Modules

I'm having a bit of an issue, and although its likely to have been discussed before, I'm having a few issues and I want to explain how far I've gotten. So I'm running an old module for friends who lived scattered across the country: Rod of the Seven Parts, which is a boxed set from the late 1990's, D&D 2nd ed.  There are a number of dungeon maps, and I'm slowly learning the roll20 interface. I recreated the starting dungeon manually.  I started doing the same for the second dungeon, but stopped for two reasons. 1) I plan to subscribe soon and use Dynamic Lighting.  (Haven't yet, but will join before long). 2) The second dungeon takes place in a cave.  Mapping a building with nice straight lines is one thing, but all the squiggly, broken angles that the game map shows is too time consuming.  So forging ahead, let's scan the map and transfer it into the game!  Only problem:  The map comes with labels like room numbers (to reference the DM to the module book) or, eventually, pits and secret doors, and other stuff you don't want the players to see.  The Game map also comes with a rusty, natural color for the floor tiles, not pure white.  So if I "erase" it using a color from the roll20 system, there's going to be a very obvious splotch on the map that can tip off the players that I covered something up.   So my next brilliant idea: Put the map on the Gamemaster's overlay layer.  I'll map out the walls with Dynamic Lighting, use roll20's colors for the floor tiles, and then /I/ can see the room numbers and traps, but the players can't!   Well, I'm having a problem with that.   I saw on a Youtube video how to adjust the grid size to match your map, and then align your map to the grid.  Great!  Except... it only allows me to do that if I paste the map on the "Map and Background" layer.  If I have the map on the GM layer, the resize grid option doesn't appear.  And if I do post the map on the "Map and Background" layer, I get the same problem with the players being able to see everything I don't want them to see.  Am I missing something?  Is there a way to put the map straight onto the GM layer for my reference, and adjust the grid tiles accordingly?  Why is it not working?  

Drop your map on the map layer to do your  tweaking and you can move it as-is to the GM layer later.  Right-Click > Move to Layer > GM

Ahhhh, that sounds like it ought to work.  Thanks!

Mark's method is how I trace out dynamic lighting on maps. If you have barriers such as crates or trees premade on the map, don't outline them but put an X in them. This allows the players to see object but still lets the dynamic lighting to do it's job. Take a look at this thread for ideas also:&nbsp;<a href="https://app.roll20.net/forum/post/3304165/dynamic-lighting-share-your-most-dynamic-setup" rel="nofollow">https://app.roll20.net/forum/post/3304165/dynamic-lighting-share-your-most-dynamic-setup</a>

How does this "X" thing work?

You use the polyline on the dynamic layer and cross two lines to look like an X in the object or you can use just a line. The Aaron shows the dynamic line usage for trees in this post:&nbsp;<a href="https://app.roll20.net/forum/category/277980" rel="nofollow">https://app.roll20.net/forum/category/277980</a>