body filler

[mojobaby]

I had a few places with surface rust that was lifting the paint. I sanded it smooth and used a rust killer and now I'm using "Mastic de Finition" or filler to smoothen the indentations made by the rust.

The stuff I've got is by Presto and hardens so quickly it's virtually unmanageable. I'd really like to know if I can add a few drops of something to retard the process or make it a bit thinner.

Someone on internet suggested acetone or lacquer thinners.
Any tips?

 

[mojobaby]

the photos that I posted are:
1) the problem
2) paint and rust stripped away and treated with rust killer
3) a somewhat messy coat of filler that still has to be sanded

It's the 3rd time that I've used filler from this particular tin. The first time it was great to work with, but now it's getting too "sticky" and is unworkable after 30 seconds

 

[snailshed]

Hi, if the tin used to be fine and now isn't something must've happened to it be it air getting in and drying / hardening it, or extreme hot or cold. I'd chuck the tin and buy new. Its cheaper than the grief of using it, messing it up, chipping it off then going to buy another tin anyway...

 

[mojobaby]

you're right. of course. Scraped the damn stuff off today and tried it again, just working a bit faster this time. I'll see what happens when I sand it tomorrow.

I think I just hate wasting; I've got half a tin left. it's probably better to prepare a few areas before I open the tin and then do them all at once.