Methylation-specific PCR is a classical & cost-effective method. However, in that bisulfite conversion and primer design will be important. You can also think of Pyrosequencing.

Article DNA Methylation Analysis: Choosing the Right Method

Cheers!!!

Bisulfite conversion of DNA remains a basic step for gene promoter Methylation analysis. Methylation analysis using set of methylated and unmethylated primer set is cost effective in individual or with few set of genes. However a Methylated control and unmthlayed control DNA should be included. These controls are commercialy available. Real time pcr or conventional PCR can be used for amplification with the primer sets

Please have a look at this paper..

https://genome.cshlp.org/content/28/1/88

A method for the determination of DNA global methylation, taken as the ratio (%) of 5-methylcytosine (5mCyt) versus the sum of cytosine (Cyt) and 5mCyt, via gas chromatography/mass spectrometry (GC/MS), was developed and validated. DNA (2.5 microg) was hydrolyzed with aqueous formic acid 88%, spiked with cytosine-2,4-(13)C(2),(15)N(3) and 5-methyl-(2)H(3)-cytosine-6-(2)H(1) as internal standards, and derivatized with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide and 1% tert-butyldimethylchlorosilane, in the presence of acetonitrile and pyridine. GC/MS, operating in single ion monitoring mode, separated and specifically detected all nucleobases as tert-butyldimethylsilyl derivatives, without interferences, with the exception of guanosine. The method was linear throughout the range of clinical interest and had good sensitivity, with a limit of quantification of 3.2 pmol for Cyt and 0.056 pmol for 5mCyt, the latter corresponding to a methylation level of 0.41%. Intra- and inter-day precision and accuracy were below 4.0% for both analytes and methylation. The matrix absolute effect, process efficiency and coefficient of variation ranged from 96.5 to 101.2%. The matrix relative effect was below 1%.